MH370: Your questions for Richard Westcott and pilot Piers Applegarth

Malaysia's prime minister has announced that missing flight MH370 crashed in the southern Indian Ocean.

Although the aircraft has not been found yet, Malaysia's Prime Minister Najib Razak said that on the basis of fresh analysis of Inmarsat satellite data it must be concluded flight MH370 has ended in the sea.

The families of the 239 people on board have been told.

The BBC's Transport correspondent Richard Westcott and Piers Applegarth, a pilot from Balpa the British Airline Pilots Association, external, have been answering your questions about flight MH370 during a Twitter Q&A.

The Q&A started before the announcement from Malaysia. Piers Applegarth continued to answer your questions following the news while Richard Westcott left the conversation to report on the latest events.

Here is an edited version of the session #AskBBCRichard - held at 13:30 GMT on Monday 24 March.

Question, external from @kopxpert tweets: Why would #MH370 be around 2,500km west of Australia? #AskBBCRichard

Richard answers, external: We don't know it's there, either went N or S. Sat data says flying for 7h+ after last radio contact & when fuel wd run out #AskBBCRichard

Question, external from @McJamweasel: Why is possible to turn the transponders off? #AskBBCRichard

Richard answers, external: 1/2: Good Q! Piers just told me the answer(s). Switch off on ground to avoid info overload (you don't need it when parked). #AskBBCRichard

Richard continues, external: 2/2: If tech prob limiting how you can fly, eg engine failed, switch off to avoid confusing flight control avoidance info. #AskBBCRichard

Richard continues, external: In other words: Computers might tell you to avoid other a/c, but ltd flight control won't let you. #AskBBCRichard

Question, external from @chris2holland: Erly rpts said MH370 climbed to 45k. If a/c decompressed would it be survivable by one pilot on oxygen?

Richard answers, external: Don't need to climb to 45k ft to decompress. Potentially, pilot could have more oxygen than anybody else. #AskBBCRichard

Question, external from @jamesmlm: Would an electrical failure on the plane have stopped life rafts deploying after a crash landing on sea. #AskBBCRichard

Richard answers, external: A: 777 don't have to carry life raft. We don't know if this one did. Slides act as life rafts. Not affected by elec. prob. #AskBBCRichard

Richard Westcott had to break away from the Q&A amid the news from Malaysia Airlines that based on Inmarsat satellite data it had to assume beyond all reasonable doubt the plane was lost and there were no survivors.

Piers Applegarth from British Airline Pilots Association continued the Q&A.

Question, external from Stirling Dutton via email: Have the Malayan authorities tried to track passengers' mobile phones? #AskBBCRichard

Piers answers, external: We don't know for sure. Staggering they wouldn't have tried. Phones don't work at 35k ft or over long stretch of water. #AskBBCRichard

Question, external from Jong-Ha Ahn via Google+: Where is the black box? Is it not working? #AskBBCRichard

Piers answers, external: Black boxes will be with plane. Transmits for 30 days and, if underwater, range 2-3km. V hard to find then. #AskBBCRichard

Piers continues, external: 2/2: One records voices, one records a/c data. Both should be working. #AskBBCRichard

Question, external from @TrickyBee: How do they know plane ditched into Indian Ocean when they have not found plane debris? #AskBBCRichard

Piers answers, external: Answer based on sat info. Before, aircraft wreckage not found for several years, although we know a/c has crashed. #AskBBCRichard

Question, external from Colin via email: If fire incapacitated pilots, can cabin crew enter cockpit? #AskBBCRichard

Piers answers, external: Cabin crew can enter cockpit. If pilots conscious they could stop door opening. #AskBBCRichard

Question, external from Marco via email: Why were passengers unable to tell from moving map if a/c going in wrong direction? #AskBBCRichard

Piers answers, external: Electrical failure, maps not working. At night, it's dark, blinds down. Can't tell direction. #AskBBCRichard

Question, external from Matthew via email: Why is black box still used rather than continuously transmit data to satellites? #AskBBCRichard

Piers answers, external: 1) You need a black box to record voices. 2) So many planes flying, it would be info overload. #AskBBCRichard

Question, external from James via text: If the aircraft travelling at 5k ft, what effect would that have on fuel burn? #AskBBCRichard

Piers answers, external: Fuel burn stays the same, but groundspeed is reduced, so less distance covered for same fuel amount. #AskBBCRichard

Question, external from @ulamamie: How did the Malaysian government conclude the missing plane was lost? Is this normal? #AskBBCRichard

Piers answers, external: Unusual not to have wreckage, but this has been known in previous accidents. Used satellite info. #AskBBCRichard

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Richard updates us on his investigations into the latest Inmarsat details:

Richard tweets, external: I've spoken to Inmarsat. They gave AAIB new calcs yesterday. It needed to be confirmed b4 going public

Richard continues, external: #MH370 it basically involved crunching far more data and totally new way of modelling..

Richard adds, external: I'm off to Inmarsat to interview the company that's helping to solve this riddle #mh370

You can follow Richard Westcott on Twitter at: twitter.com/BBCwestcott, external

Twitter Q&A produced by Richard Irvine-Brown and Sitala Peek