A few pieces of MH370, a Boeing 777-200ER, have recently been found on a Mozambique beach, and confirmed as authentic parts.
Their excellent condition and relatively large sizes indicate that the accident wasn’t a high-speed impact with an obstacle or water.
As a commercially-rated airplane pilot, my opinion is that leaves:
- explosion or decompression
- descent (or phugoid) into ocean at relatively low speed
- “graveyard spiral dive” pulled the wings off.
An interesting question would be, “In modern airliners, especially Airbus, anti-phugoid software is deployed. How would that affect an uncontrolled airliner?” Sully said that anti-phugoid software in his Airbus prevented him from slowing descent before impacting the Hudson River.
MH370 Debris Storm
Tourist who found debris was searching for MH370
Australia Confirms Mozambique Debris Came from MH370
MH370: Debris found in March ‘almost certainly’ from missing plane
Investigators Report On MH370 Debris Analysis (2016)
ATSB MH370 Report [pdf]