By David Shepardson and Tracy Rucinski

“This recommendation takes into account our unstinting commitment to the safe return of service as well as changes to the airplane and test results. Final determination will be established by the regulators,” Boeing said in a statement.

In a separate statement, the Federal Aviation Administration said it will consider Boeing’s recommendations during upcoming evaluations of U.S. and international flight crews meant to help the FAA and other regulators assess 737 MAX training needs.

If simulator training is ultimately recommended, it could take airlines even longer to prepare their crews to fly the 737 MAX once regulators lift a grounding that has gone on for 10 months after two crashes within five months that killed 346 people.

Boeing has been working on revised pilot training and software updates for the 737 MAX to win approval for the jets to fly commercially again.

U.S. and European aviation safety regulators are meeting with Boeing this week in an effort to complete a 737 MAX software documentation audit – an important step toward the grounded plane’s eventual return to service.

The planemaker had said in March it would propose requirements for pilots that did not include costly flight simulator training.

The level of pilot training for the 737 MAX, an updated version of Boeing’s 737 narrowbody workhorse, was a concern for airline customers that considered purchasing the new aircraft that first launched in 2016.

At a Congressional hearing in October that focused on the 737 MAX crashes, U.S. lawmakers said Boeing had reassured Southwest Airlines Co, its largest customer, that simulator training would not be needed and backed up the promise with a $1 million per plane rebate if such training were necessary.

Southwest, which is cancelling more than 150 daily flights into April without the 737 MAX in its fleet, has said it would require all of its more than 9,500 737 pilots to undergo new MAX training. If only computer-based training were required, the process was expected to take one to two months.

Not many 737 MAX simulators currently exist.

Southwest had not been part of Boeing’s recent discussions on pilot training recommendations, spokeswoman Brandy King said. Southwest has three 737 MAX simulators in various stages of FAA certification and expects three more later this year.

American Airlines Group Inc, Boeing’s second largest U.S. customer, only has one 737 MAX simulator, while United Airlines expects its first 737 MAX simulator in coming weeks.

It was not clear if any simulator training could be performed on previous 737 simulator models, or whether airlines with large 737 fleets could initially decide to train only some of their pilots on the MAX.

Boeing shares were up 1% on Tuesday, reaching a 3-week high following unconfirmed reports that Warren Buffett’s Berkshire Hathaway is buying the company’s stock. (Reporting by David Shepardson and Tracy Rucinski Editing by Bernadette Baum and Bill Berkrot)