The FAA now expects to decide by the end of the year on a technical fix that Boeing has proposed to clear up pilot confusion about 737 altitude warning horns.
In September, the agency said it had hoped to make a decision by October, but it now is waiting for Boeing to verify that its proposed fixes will work for all 737 models.
The in-flight altitude warning horn, the device 737s use to warn pilots of a problem with cabin pressurization, is also used to warn pilots while still on the ground if their aircraft is not properly configured for takeoff.
As Travel Weekly reported in April, 737 crews for more than a decade have been mistaking the altitude horn for a malfunctioning takeoff warning while in flight.
Earlier this year, the FAA required additional crew warnings about the horn's significance, along with a permanent mechanical fix. Boeing said it was working on a new horn system for newer planes and a retrofit solution for older 737s.
The FAA said the extra warnings and training that airlines began giving cockpit crews this spring appeared to be working. The agency said it was not aware of any incidents since September and only one "report indicating a several-second delay in recognition" since the agency took interim measures to help remind pilots about the dual function of the horn.
In that case, the FAA said, crew members took prompt and appropriate action once they recognized the horn's meaning.
The FAA said it was closer to ruling on the proposed Boeing fixes for older and newer generation models.
"We have the service information for the 737 Classic, and we completed our review," it said in an email.
The FAA said it reviewed the 737NG preliminary fix but was waiting for Boeing to make sure the plan was "sufficiently clear and detailed" to work as intended.
"We expect to approve the service information for both the classic and the [new-generation aircraft] by the end of the year," the FAA said. "Once that is done, we plan to take one common rule-making action for both fleets."
