REUNION ISLAND (Bloomberg) - Malaysian Prime Minister Najib Razak has confirmed that a jet part found on an island near Africa came from Malaysia Airlines' flight 370, the first physical evidence from the jetliner that vanished almost 17 months ago.
Investigators "conclusively" linked the piece to the missing aircraft, Datuk Seri Najib said on Thursday. A French prosecutor stopped short of that assessment, saying only that officials have a "strong presumption" that the debris being studied in a government laboratory is from the doomed plane.
With the families of those on board eagerly awaiting any information on what happened to MH370, here are five key questions from the finding that may help shed light on the fate of the missing plane.
1. Does the plane part tell us where MH370 is?
If the plane part confirms that the plane crashed in the Indian Ocean - but not much more than that. For all the uncertainties around the satellite data that investigators used to project the plane's final path, it's still a more precise science than modeling of ocean currents.
Reunion island is some 3,800km from the isolated spot of ocean where satellite data suggest the plane crashed. That sounds like a long way, but it's not surprising to oceanographers.
"The distance is not a problem. Things can easily go that distance in this amount of time," said Mr David Griffin, an oceanographer for Australia's government scientific institute CSIRO who has modeled potential paths of drifting wreckage for the MH370 investigation. "We've always thought Madagascar was a likely area. This is north of that, but we're still within the realm we expected."
CSIRO's studies of ocean currents and wind effects confirm that material from the area where flight 370 is assumed to have crashed could have made its way to Reunion, according to Mr Truss.
Based on the Australian Transport Safety Bureau's analysis, individual analytical methods can produce different results about where the plane ended up. Based on the aircraft's fuel load, it could have made it to almost any point in the Indian Ocean and a swathe of central, southern and eastern Asia.
Communications with an Inmarsat satellite suggest a different group of locations. One of the only places where these different methods converge is in the current search zone.
2. How long has the part been in the water?
Barnacles seen clinging to the wreckage in photographs of the flaperon may help trace its path. Species of the small arthropods can be traced to different regions of the world, according to Dr William Newman, an emeritus professor at the Scripps Institution of Oceanography in La Jolla, California.
They also can help confirm when the flaperon entered the ocean, according to Newman. Many species of the crustaceans leave growth rings on their shells - a fact recognised by Charles Darwin in an 1851 monograph - which can help give a ballpark figure of how long an object has been submerged.
There also may be suggestive evidence in the structure of the flaperon itself. The corrosion rates of different metals are fairly well understood. One test on the coast of North Carolina found it took just a year for damage to penetrate about one- hundredth of an inch into a welded piece of 6061, an aluminum alloy frequently used in aircraft parts.
3. How did it break off?
The specific nature of damage is often crucial evidence in examining aircraft wreckage.
The investigation into the 2009 crash of Air France 447 found an elevator - a type of control flap from the plane's tail - floating in the Atlantic Ocean. Four places where it was attached to the tail were torn as if a force had struck them from below, according to an interim report - a clue that the plane had struck the water belly-down.
Looking at the cracks where the flaperon was torn loose from the aircraft may help explain how the metal broke and what caused it, according to Mr Jim Wildey, former chief of the US National Transportation Safety Board's materials laboratory - provided salt water hasn't corroded the tell-tale signs.
Even if there's no visible evidence, scanning the part under an electron microscope may show distinctive features, according to Mr Geoffrey Dell, a discipline leader in air accident investigations at Central Queensland University.
Pictures of the flaperon suggest it wasn't badly damaged, according to Mr Wildey. One explanation for that would be that the crash came at lower speeds than some of the most violent impacts that can destroy an aircraft.
All that could help determine whether the flaperon came off the aircraft in mid-air, or was shorn off when it hit the water, helping provide clues to the flight's final moments.
4. What position was it in when the plane went down?
One of the central mysteries around flight 370 is the degree to which the incident was intentional. Mr Najib has said the plane was deliberately steered off-course, and investigators have concluded that someone on board disabled the plane's tracking devices.
Still, flight 370's presumed six-hour final journey on a straight path south across open ocean has been taken as evidence that it was on autopilot in its last moments.
"Our assumption, based on the evidence available to us, is crew incapacitation," Mr Martin Dolan, commissioner of the Australian Transport Safety Bureau, said in a March interview. "There was no one actually at the controls."
That makes the failure to find the plane in the seafloor search conducted since last October confounding. The ATSB has assumed the aircraft spiraled into the sea and crashed somewhere within a 10 nautical-mile radius of the point where its fuel ran out. With no wreckage found, they're now extending the radius to cover the possibility that the 777 glided further, at a more shallow angle, before crashing.
Such a scenario is possible, but long glides are easier to carry out with a pilot at the controls. Any evidence suggesting whether the flaperons were up in flying position, or down in landing position, could help resolve that issue.
In the unlikely event that a pilot was conscious and attempting a gradual water landing, they would have lowered the flaperons to slow their rate of descent. Parts of the wing mechanisms can leave impact marks that can show whether flaps or flaperons were up or down, as happened with Flight 447.
That may help the underwater investigation as well.
Mr Paul Kennedy, who's leading the seabed search for contractor Fugro NV, said in March: "It really comes down to, 'Was there a human gliding it?'"
For the families of those on board, the investigation in France is likely to leave plenty of unanswered questions.