Boeing Co is expected as early as Monday to formally disclose a planned upgrade to its anti-stall system to the Federal Aviation Administration (FAA) that has been in the works since October's Lion Air crash but still needs approval from USA regulators.
The Allied Pilots Association (APA), which represents American Airlines pilots, said it has been in talks with Boeing, the FAA and airlines to get the airplanes flying again as soon as possible, albeit with an acceptable level of safety.
FAA spokesman Lynn Lunsford declined to comment, citing an open investigation.
The update involves tweaking the system created to prevent an aerodynamic stall if sensors detect that the plane's nose is pointed too high.
On Friday, CNN said in a report that pilots from Southwest Airlines and American Airlines took courses lasting between 56 minutes and three hours when moving between the two Boeing models. He says that having only USA doing investigation might affect the objectivity of the investigation since there is "little independence and stakeholder confidence".
"We've been working diligently and in close cooperation with the FAA on the software update". And Boeing said recently that the new flight system would also be accompanied by new crew training related to the MCAS, which was viewed as a major departure from its earlier policy on the matter.
"There will be training provided by Boeing".
Teams from USA airlines Southwest, United Airlines and American Airlines that own 737 MAX jets went to Boeing Co's factory in Renton, Washington, to review the software upgrade on Saturday, as the FAA prepares to receive and review the fixes.
In another modification, the 737 MAX will be outfitted with a warning light for malfunctions in the anti-stall system, an industry source told AFP on Thursday, standardizing a feature previously sold as an optional extra.
Ethiopian Airlines is widely seen as Africa's best-managed airline.
Since the Ethiopian crash, pressure has intensified on Boeing and the image of the company - which also makes combat aircraft and space equipment - has been eroded.
The acting FAA head is among transport officials who are to testify on Wednesday before a congressional subcommittee.
Ralph Nader, the veteran United States consumer protection advocate who lost a relative in the Ethiopia crash, called Friday for an organization to defend passengers' rights.