CHICAGO (Reuters) - American Airlines pilots have warned that Boeing Co’s draft training proposals for the troubled 737 MAX do not go far enough to address their concerns, according to written comments submitted to the U.S. Federal Aviation Administration and seen by Reuters.

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The comments were made by the Allied Pilots Association (APA), which represents pilots at American Airlines Group Inc, the world’s largest airline and one of the biggest 737 MAX operators in the United States.

Their support is important because Boeing has said pilots’ confidence in the 737 MAX will play a critical role in convincing the public that the aircraft is safe to fly again.

Boeing’s fast-selling 737 MAX was grounded worldwide in March following a fatal Ethiopian Airlines crash that killed all 157 on board just five months after a similar crash on a Lion Air flight that killed all 189 passengers and crew.

Now it is readying for regulatory approval a final software update and training package to address an anti-stall system known as MCAS that played a role in both nose-down crashes.

A draft report by an FAA-appointed board of pilots, engineers and other experts concluded that pilots only need additional computer-based training to understand MCAS, rather than simulator time. The public has until April 30 to make comments.

Protesters are expected outside Boeing’s annual meeting in Chicago on Monday, where shareholders will also question the company over its safety record.

APA is arguing that mere computer explanation “will not provide a level of confidence for pilots to feel not only comfortable flying the aircraft but also relaying that confidence to the traveling public.”

It said the MAX computer training, which originally involved a one-hour iPad course, should include videos of simulator sessions showing how MCAS works along with demonstrations of other cockpit emergencies such as runaway stabilizer, a loss of control that occurred on both doomed flights.

APA also called for recurring training on simulators that includes scenarios like those experienced by the Lion Air and Ethiopian Airlines pilots, in addition to computer training.

“When pilots visually experience the failure modes and then apply them, the lesson is cemented in their minds,” APA wrote.

American Airlines has said it is looking at the potential for additional training opportunities in coordination with the FAA and its pilots union.

Canada, Europe and South Korea are all weighing the need for simulator training, going above the recommendations in the draft FAA report, sources have said.

Required simulator training could delay the MAX’s return to service because it takes time to schedule hundreds or thousands of pilots on simulators. Hourly rates for simulators range between $500 and $1000, excluding travel expenses.

American Airlines Chief Executive Doug Parker said on Friday that even if other countries delay the ungrounding of the MAX, once the FAA approves it, American will start flying its 24 aircraft.

Union pilots for Southwest Airlines Co, the world’s largest operator of the MAX with 34 jets and dozens more on order, have said they were satisfied with the FAA draft report but would decide on additional training once they see Boeing’s final proposals.