Indonesian investigators said the cockpit recording from the crashed Lion Air jet showed the pilots searching a manual to try to find why the plane kept lurching downwards.
The details were revealed at a press conference, where an investigator said the recording captured a "panic" in the cockpit in the last 20 seconds of the flight.
They are looking into how a computer ordered the plane to dive in response to data from a faulty sensor and whether the pilots had enough training to respond to the emergency.
The investigation has taken on new urgency after a second 737 MAX 8 crash at Ethiopian Airlines last week killed 157 people and led to the global grounding of the model.

Malaysia ex-PM Najib jailed for 15 more years in 1MDB case
US launches strike against ISIS in northwest Nigeria
Israel formally recognises Somaliland as independent state
Explosion at mosque in Syria's Homs kills eight
Ukraine president discusses "bringing peace closer" with US negotiators
