Good morning. We're continuing our live coverage today of the search for possible wreckage from missing Malaysia Airlines flight 370 in the Indian Ocean off Perth.

The aerial search was called off late on Thursday night, with no sightings of the debris identified earlier on a US satellite image.

The first plane is due to take off again at 5.30am this morning in Perth, which is 8.30am eastern daylight time.

What exactly are they searching for?

Search teams are hoping to find two objects, one measuring roughly 24 metres in length and the other about five metres in length, that were captured on US satellite images on Sunday.

Those images had been analysed by satellite experts from the Australian Geospatial Intelligence Organisation, which deemed them "credible sightings".

The area where the debris was sighted is about 2500 kilometres south-west of Perth.

The latest update from AMSA, issued late on Thursday night, says four aircraft involved in Thursday’s search covered a search area of about 23,000 square kilometres.

A Norwegian merchant ship arrived in the search area on Thursday evening, while another merchant ship is en route to the area.

The Royal Australian Navy ship HMAS Success has also set off from Fremantle, but is expected to take two days to reach the area.

AMSA search operations for #MH370 have been completed for today, the search will continue in the morning. More here http://t.co/PQ7XndbKLQ — AMSA News (@AMSA_News) March 20, 2014

Here you can find a rundown of how the news broke on Thursday afternoon, and how the search unfolded throughout the afternoon and into the night.

Weather will be a key concern for the Australian-led search team today.

Rough seas, high winds and poor visibility in the southern Indian Ocean hindered the operation on Thursday, and search teams were unable to locate any debris.

But conditions are expected to ease into the weekend, Weatherzone meteorologist Rob Sharpe says.

As David Wroe writes, the satellite images were taken on Sunday and the debris could already have floated scores of kilometres away, making the search even more difficult.

The Australian Maritime Safety Authority has explained why authorities are only now acting on the images, which the Australian government has said came from a commercial satellite.

"Due to the volume of imagery being searched, and the detailed process of analysis that followed, the information was brought to the attention of the Australian Maritime Safety Authority on Thursday morning," it said.

One of the planes scouring the southern Indian Ocean on Thursday afternoon did detect several objects on its radar - but it turned out to be a false alarm.

One was a freighter, and two others were pods of dolphins.

David Wright, from US news organisation ABC, was on board the P-8 Poseidon plane that was sent to the area where debris from the airplane was potentially identified.

Wright said searchers were posted at all of the plane's windows, and the plane worked back and forth through its search area in a ‘‘lawn mowing pattern’’.

Nada today - except for a freighter and 2 pods of dolphins. They'll be back out tomorrow - eager to provide answers to those families #MH370 — David Wright (@WrightUps) March 20, 2014

The Age's Steve Lillebuen has contacted Norwegian cargo ship Höegh St Petersburg, which has been diverted to the search area.

But the skipper declined to answer any questions about the search or current weather conditions, referring inquiries to AMSA.

An AMSA spokeswoman had no further updates.

The Höegh St Petersburg, a car carrier, was en route from South Africa to Australia when it was diverted.

Other vessels heading to the search zone include the Australian navy ship HMAS Success, which is due to reach the area on Saturday.

Fairfax Media reporter Patrick Hatch reports that seven Victorian State Emergency Service (SES) volunteers have flown to Western Australia to help search for the missing flight.

SES spokeswoman Sally Lowenstein said the volunteers had been trained as air observers by the Australian Maritime Safety Authority, and flew out of Essendon Airport on a search-and-rescue plane about 5am on Friday.

“That plane is based in Victoria and that’s why they’ve taken a Victorian crew as well,” she said.

The volunteers will work from RAAF Base Pearce, north of Perth, until Wednesday.

At 8am, the Australian Maritime Safety Authority released this update about today's operation:

"Today’s search will utilise four military aircraft, including two RAAF Orions, tasked by the Australian Maritime Safety Authority (AMSA) to search a 23,000 kilometre area, about 2500 kilometres south-west of Perth.

"A merchant ship remains in the search area. Another merchant ship is en route to the area and is expected to arrive tonight.

"A total of six merchant ships have assisted in the search since a shipping broadcast was issued by AMSA on Monday night."

So remote is the search zone, in the Indian Ocean 2500 kilometres south-west of Perth, that it takes aircraft about four hours to reach the area.

When they arrive, they only have enough fuel to search for two hours, before heading back to base.

This video shows what flight crews are confronted with:

Peter Hartcher reports that, when the Australian official took the podium to explain to reporters the discovery of satellite images that might show pieces of MH370, he carefully omitted to tell them the source.

The images were from a US satellite. The Australian Maritime Safety Authority's John Young didn't mention this to the media. Nor was he asked. But he wouldn't have disclosed it in any case.

As ever, Australian officialdom is hyper protective of US intelligence and its sources - even more protective than the Americans themselves.

Norwegian car carrier Höegh St Petersburg on Thursday night reached the Indian Ocean area where possible debris of the missing Malaysia Airlines MH370 plane was spotted.

"The ship has arrived at the site to take part in the search," said Cecilie Moe, spokeswoman for the Norwegian company.

According to another Hooeg Autoliners spokesperson, Christian Dahll, the search window for Thursday was limited by sunset.

The "St. Petersburg" vessel, a vehicles carrier, was on its way from Port Louis in Mauritius to Melbourne, when it was requested by the Australian authorities to reroute in order to identify the debris spotted by satellite in the southern Indian Ocean.

The search team is facing an incredibly tough task, as Fairfax Media's science editor Nicky Phillips explains.

The area of ocean being scoured is close to the Roaring Forties, a region where strong westerly winds whip up giant swells and waves, creating some of the roughest seas in the world.

There is almost no land to slow the winds, which creates strong, high waves and swell.

The currents also extend through the water column as the region is so deep.

It is an area that ships tried to avoid, unless they are travelling from South Africa to Tasmania.

If the debris in the southern Indian Ocean is confirmed to be from Malaysia Airlines flight MH370, it would eliminate some of the wilder theories about what happened to the plane, writes Anne Davies.

It would point instead towards the likelihood of an emergency on the flight, and an attempt by the crew to turn back and complications that caused them to fall into unconsciousness, leaving the plane on a ghost flight until it ran out of fuel.

The first search plane took off from Pearce RAAF base in Western Australia at 6.15am Perth time on Friday, which is 9.15am eastern daylight time.

Four planes will be involved in today's search, and their departure times will be staggered throughout the day.

The next plane is due to leave at about 8am Perth time, or 11am eastern daylight time.

It takes about four hours for the aircraft to reach the search zone.

Search planes have started to leave Pearce Air Base to search for possible debris that may belong to #MH370. #Perth pic.twitter.com/0z7JGt1IjY — Grace Millimaci (@GraceMillimaci) March 20, 2014

One of the world’s top air accident investigators says the missing Malaysia Airlines jet may never be found if it came down in the Indian Ocean, according to the Financial Times.

Rémi Jouty, head of the Bureau d’Enquêtes et d’Analyses, the French air accident investigation branch, said much more work was needed before any undersea search could start if debris did indeed turn out to be from the missing aircraft.

“The only thing I can say is it will be most difficult and the recovery [of the wreckage on the seabed] is not guaranteed,” Mr Jouty told the Financial Times.

Weather conditions appear to be quite bad at Pearce RAAF base, near Perth, this morning. That's where the search planes are setting off from.

Had very strong rain and wind storm move through RAAF Base Pearce this morning. Here's what's left of our tent. pic.twitter.com/4UoMPs1vZs — Oliver Janney (@CNNewsCrew) March 20, 2014

Prime Minister Tony Abbott was in Port Moresby on Friday morning, and said that Australia was ‘‘throwing all the resources we can at it [the search operation]’’.

‘‘We will do everything we humanly can to try to get to the bottom of this,’’ he said.

‘‘We don’t know what that satellite saw until we can get a much better, much closer look at it but this is the first tangible breakthrough in what up until now has been an utterly baffling mystery.

‘‘We do have pretty strong satellite imagery and obviously this is a very serious lead in the way that nothing else so far really has been.’’

AMSA has just released its latest update, stating that two more aircraft were due to depart for the search area a short time ago, at 11am AEDT.

The civil Gulfstream jet and a second RAAF P3 Orion will take over the search from the RAAF P3 Orion that set out at 9.15am AEDT.

Due to the distance to and from the search area (about a four-hour flight each way), each aircraft will only have about two hours of search time.

AMSA says a total of five aircraft will be involved in today's search, with a third RAAF P3 Orion due to depart about 1pm AEDT.

A United States Navy P8 Poseidon will set off for the search area about 4pm AEDT.

One merchant vessel is currently in the search area, with a second due to arrive tonight.

Prime Minister Tony Abbott is set to hold a press conference in Papua New Guinea about lunchtime, our reporter David Wroe says. Mr Abbott is expected to outline further details about the search.

The Norwegian cargo ship Hoegh St Petersburg was the first ship to reach the search area.

It searched through the night, even though the official search was called off.

The CEO of Hoegh Autoliners, Ingar Skiaker, has told reporters from Oslow that "we consider this an emergency situation and we will continue until further notice".

"If there [are] any survivors spotted, we will have the means to take them on board," he said.

The search for potential wreckage in the southern Indian Ocean is painstaking. But the wait for families of those on board Flight MH370 must be agonising.

Families huddled around television screens on Thursday as news broke that possible debris from the plane had been spotted.

"It gets your heart racing ... I will tell you that, but it could just be nothing. We don't know and neither do they,’’ said Sara Weeks, whose brother Paul Weeks was aboard the missing flight.

A photographer due to take off on a search plane from Pearce RAAF base on Friday morning has reported a lot of lightning over the area.

"It's windy, it's wild, the media are having terrible trouble with keeping their kits up," said photographer Bohdan Warchomij.

Fairfax Media reporter Peter Hannam has spoken to Ben Domensino, a senior meteorologist with Weatherzone, who says weather conditions over the search area look likely to improve for a couple of days at least.

Domensino says a high pressure ridge will be passing to the south of the search area over the weekend. This will allow wind and seas to ease and allow some clearing, which would help the search effort.

Another trough may move back into the region early next week, around Tuesday or Wednesday. This should bring more cloud and rain and cause wind to increase

Fairfax Media journalist Liam Ducey was on board an RAAF Hercules aircraft as it scoured a stretch of ocean off Australia’s west coast. Here he writes of the ongoing search for missing Malaysia Airlines Flight 370.

Here's a useful graphic from the Wall Street Journal about the sea and air convoy from 12 countries committed to the search in the southern corridor.

AMSA has also just released an updated map of the area to be searched today.

Here's a map from the AMSA showing the cumulative area searched since Tuesday.

This is the satellite that captured the images that may be of debris related to missing Malaysia Airlines flight 370.

WorldView-2, owned by US satellite company DigitalGlobe, provides imagery at a resolution of approximately 50 centimetres. It takes a new image of any place on earth every 1.1 days (one day, two hours and 24 minutes), writes deputy technology editor Ben Grubb.

DigitalGlobe confirmed on Friday that it was the one that provided the Australian Maritime Safety Authority (AMSA) with the satellite images that were captured on March 16, showing the two objects in the Indian Ocean.

"We have been informed by an Australian government official that it was our imagery Prime Minister [Tony] Abbott referred to in his recent comments," the company said in a statement.

Read the full story. 

Investigators seeking the missing Malaysia Airlines plane face a "colossal task" that is "far, far harder" than the two-year search for an Air France jet that crashed into the Atlantic, the man who led the French inquiry has warned.

Alain Bouillard's comments came as experts described the deep waters of the Southern Ocean that may contain debris belonging to flight MH370 as "one of the most hostile environments in the world".

Mr Bouillard, 63, worked for France's air accident investigation bureau, BEA, a world authority on air crashes, and also led the investigation into the Concorde disaster outside Paris in 2000. Three BEA members are helping the Malaysian authorities in their search.

"This disappearance is still a great mystery, and will lead to an inquiry and a search that is far, far harder than we had looking for Air France 447," Mr Bouillard said.

Read the full story. 

The head of shipping at Hoegh, Olav Sollie, said that those on board the ship would not necessarily be using fancy technology in their search efforts.

"The best way with this size of a vessel [which is 230 metres long], it sounds probably old-fashioned, but it's a very good way of doing a search on sea, that is on deck with a binocular."

Tony Abbott is continuing his first trip to PNG as Prime Minister.

He has just done a press conference, where we learn that he has called his Chinese counterpart to give him an update on MH370. 

PM Abbott has called Chinese Pres Xi Jinping to update him on the situation with #MH370. "If there us anything down there, we will find it" — Karen Middleton (@KarenMMiddleton) March 21, 2014

We will bring you more from the PM's Port Moresby press conference shortly.

But first, more information has emerged about the satellite search for the missing Malaysia Airlines Boeing.

The Herald's Ben Grubb reported today on the US satellite that captured the images of the debris 2500 kilometres south-west of Perth.

And The Washington Post writes that the United Nations activated an international consortium of space agencies and satellite companies to scan the oceans for clues.

"The Space-based Information for Disaster Management and Emergency Response, known as UN-SPIDER, is a collection of space agencies and commercial satellite companies, including the one that spotted the objects off the coast of Australia.

"Normally, UN-SPIDER is activated after floods, earthquakes, volcano eruptions and other natural disasters. This is the first time since UN-SPIDER was formed that its members have been mobilised to find a missing airplane, according to the UN-SPIDER Web site."

Fairfax China correspondent Philip Wen has been at the Lido Hotel in Beijing, where the families of some of the passengers on board MH370 are staying.

He reports they have spent the morning being briefed by a senior Malaysian delegation - sent by Malaysian PM Najib Razak - that arrived on Thursday night.

They included representatives from the Malaysian defence force, civil aviation authority and a Boeing 777 pilot.

Not much new information being discussed, much to everyone's frustration. — Philip Wen (@PhilipWen11) March 21, 2014

The delegation was sent after satellite data showed that the plane had likely flown for hours after it went missing.

Philip Wen also reports that families have questioned why it took so long to verify the data.

(This follows a Wall Street Journal report that officials took four days to act on the satellite information that showed the plane had flown for several hours away from the area being covered.)

Four aircraft have now left Perth for the search area in the southern Indian Ocean, AMSA has announced.

A RAAF P3 Orion left at about 12.45pm (Australian Eastern Daylight Savings Time).

It will join two other P3 Orions and an ultra long range Bombadier Global Express jet.

A US Navy P8 Poseidon plane will leave at about 4pm.

AMSA says that, due to the distance to and from the search area, the aircraft involved have about two hours of search time.

As others have also pointed out, the PM's early-announce approach with the debris-find also avoids being tarred with the same brush as Malaysian authorities.

It's been put yo me PM Abbott had to act quickly to prevent type of criticism Malaysia getting for not releasing information. — Malcolm Farr (@farrm51) March 21, 2014

AMSA's website has been straining under the increased interest now that it is spearheading the search effort for MH370.  

It has been down on and off today.

AMSA spokeswoman Lisa Martin says the reason ASMA's website has often not been accessible is due to the fact it had been inundated with visitors, especially by people in the media.

"Normally there are only 30 people active on it at any one time. Now there are around 1000 at any one time," she said, adding that AMSA's Twitter following has increased by 10,000 followers overnight.

China is sending some warships!

AP reports that China is sending three ships to search for the possible pieces of the Malaysia Airlines plane, the government said today.

It has not been reported where the ships are coming from, or when they might arrive.

However, previous reports have said that ships have been searching near Sumatra.

Funny, but Tony Abbott did not mention this after his conversation with Chinese President Xi Jinping.

We know that a satellite owned by US company DigitalGlobe took the images of the missing debris.

But who provided them to AMSA?

Ben Grubb reports that:

Spokeswoman Lisa Martin has told Fairfax Media that Australian intelligence agency, Defence Imagery and Geospatial Organisation, provided AMSA with the satellite imagery from March 16 that shows two objects in the Indian Ocean.

She said DIGO was scouring through DigitalGlobe's imagery and not AMSA. She did not know how many personnel at Defence were looking over the imagery.

It is about a 7 hour round trip from Perth to the search area by air (depending on weather conditions).

The aircraft have about 2 hours of search time when they get there.

That means that the first plane that set out this morning at 9.15am (Australian Eastern Daylight Savings Time) should now be on its way back.

The planes that left around 11.15am and 11.30am should have reached the search area by now.

The fourth plane, which left at about 12.45pm would almost be at the search area.

A fifth plane is due to leave Perth at 4pm.

According to AMSA, the planes can communicate back while they in the search area if they should find anything.

As the hunting and waiting continues, National Affairs editor Tom Allard writes on the five air safety lessons to be learned from the missing Malaysia Airlines plane.

• How could an aircraft vanish when there are websites that track planes in real time?
• When countries co-ordinate a search mission, they're not always sharing information;
• Why doesn't the black box float?
• There are big gaps in the global airworthiness alert system; and 
• Passport control is not as watertight as we'd like to think.

Fairfax China correspondent Philip Wen has been at the Lido Hotel in Beijing where the families of passengers on board the missing plane have been briefed by a Malaysian government delegation.

He notes that there is an "even heavier" police presence there than yesterday.

And that media were ejected from today's family briefings.

Lots of resentment toward Malaysian handling of plane crisis, this Malaysian delegation could be used as punching bag. — Philip Wen (@PhilipWen11) March 21, 2014

We are going to now suspend live coverage as we await news from the search zone.

A quick wrap of what happened today.

The first plane left Perth at about 9.15am. Now four other planes have either reached the search area or are on their way there.

A Norwegian merchant ship has also been searching the area, 2500km southwest of Perth, since Thursday night, with another due to arrive tonight.

So far, nothing has been found.

Meanwhile, Prime Minister Tony Abbott has defended his decision to announce the potential breakthrough yesterday in parliament, saying Australia "owed it" to the families of those on the missing plane to give them information as soon as it comes to hand.

The blog will resume if major news breaks.

You can watch a video of the Hoegh company press conference below.

There have been some eyebrows raised about the fact that Tony Abbott made his announcement to parliament about the debris before any effort could be launched to find it.

But as we noted earlier, he made a passionate defence of the way he played things, when asked in a press conference in PNG.

He said that not only did Australia owe it to the families of those on board to "do everything we can to solve this",

"[we] owe it to them to give them information as soon as it's to hand".

The Age's political editor Michael Gordon is travelling with the Prime Minister in PNG.

While Tony Abbott's press conference obviously dealt with Manus Island issues, the missing plane was also discussed.

Michael reports that, given there have been no sightings of any debris possibly linked to the missing plane, the PM gave a passionate defence of his decision to make a statement to Parliament on Thursday on the discovery of the satellite images.

He said we all owed it to the loved ones of those missing to crack this "extraordinary riddle".

Mr Abbott described the search as a "gut-wrenching business" and acknowledged that what was shown in the images could potentially be a discarded shipping container.

He also described the search area as the most inaccessible spot one could imagine on the face of the planet.

Here's a video from RAAF Base Pearce north of Perth, where the planes are leaving from.

AKA "the waiting game".