There was another flight that was lost in the Indian Ocean in 1987. Controversy surrounded it as well.

The Boeing 747-244B Combi was a variant of the aircraft that permits the mixing of passengers and airfreight on the main deck according to load factors on any given route and Class B cargo compartment regulations Flight 295 had 140 passengers and six pallets of cargo on the main deck. The master waybills stated that 47,000 kilograms (104,000 lb) of baggage and cargo were loaded on the plane. A Taiwanese customs official performed a surprise inspection of some of the cargo; he did not find any cargo that could be characterized as suspicious.

The flight crew consisted of:

49-year-old Captain Dawid Uys (who had 13,843 flight hours)
36-year-old First Officer David Attwell (who had 7,362 flight hours)
37-year-old Relief First Officer Geoffrey Birchall (who had 8,749 flight hours),
 45-year-old Flight Engineer Giuseppe Bellagarda (who had 7,804 flight hours), 34-year-old Relief Flight Engineer Alan Daniel (who had 1,595 flight hours). 

This was the cockpit recorder. (click here) The reason I thought this particular jet relevant is because this is the deepest a recorder that has been recovered at 4,900 metres (16,100 ft). The flight recorder reasonably survived that depth of ocean.

I also thought it relevant because even after the aircraft was found there continued to be controversy regarding this crash. There is a website dedicated to that controversy itself.

The Helderberg: Mystery (click here) 

 ...So the existence of a cover-up is almost without question - and a judicial cover-up by Judge Margo at that. However don't confuse this aftermath intrigue and threats to persons with the cause of the accident itself. It could very likely have been a wiring-initiated fire but the ramifications of it having brought the plane down necessitated an emergency concealment of not only the type of cargo, but the fact that SAA had been sanctions busting for years in this way. If this had been publicly revealed, then SAA would have lost many of its routes and destinations. A very similar cover-up was carried out by Air NZ after the Mount Erebus DC-10 disaster - simply because they quickly became aware that the accident had been caused by the airline's latest navigation software upload...

The ultimate cause of the crash of the Helderberg was fire that was smoldering for some time before it actually took the aircraft from the sky, but, the political controversy still continued. 

When the Prime Minister makes his statement later today regarding  Malaysia Airlines flight MH370 and the jet is considered officially lost the inquiry won't end. The search won't end. The investigation won't end. It can't. Deaths of human beings require conclusion and until that is satisfied the loss of these people will remain on the radar for decades if not centuries. Someday the evidence of it's final hours will be realized. The oceans are mysterious structures of Earth, but, rarely do they ever conceal it's mystery forever.