Read the full story as pressure mounts on Boeing and the FAA.
Boeing 737 Max 8
American Airlines pilots confronted Boeing about concerns regarding the Boeing 737 Max, the model that crashed in Ethiopia on March 10, US media has reported.
A meeting took place in November last year following a crash in Indonesia that killed 189 people.
Pilots said they hadn't been fully informed about the new anti-stall system, which investigators say may have caused the crashes.
Boeing promised to make changes to software but this was still in progress when the Ethiopian Airlines plane crashed and killed all 157 people on board.
The 737 Max is currently grounded worldwide.
Virgin Australia has said it has reached an agreement with Boeing to defer the delivery of its first Boeing 737 Max jets to mid-2021 from late 2019.
Boeing grounded its entire global fleet of 737 Max aircraft in March following a second fatal crash involving the 737 Max 8.
"We will not introduce any new aircraft to the fleet unless we are completely satisfied with its safety," said Paul Scurrah, Virgin Australia chief executive, in a statement.