UPDATE 1-U.S. FAA says it expects to receive Boeing software fix over 'coming weeks'

The U.S. Federal Aviation Administration (FAA) said on Monday it expects to receive Boeing Co's proposed software enhancement package for the grounded 737 MAX "over the coming weeks" after the company had previously said it planned to submit the fix for government approval by last week. FAA spokesman Greg Martin said that "time is needed for additional work by Boeing as the result of an ongoing review of the 737 MAX Flight Control System to ensure that Boeing has identified and appropriately addressed all pertinent issues."

Southwest Airlines said on Monday it is "publishing a revised schedule for April and May that is built around the currently available Southwest fleet and intends to reduce drastically last-minute trip disruptions and same-day cancellations." Boeing did not immediately comment on the FAA's statement. The company said earlier on Monday that it continues to work with the FAA and "other regulatory agencies worldwide on the certification of the software update and training program."

Boeing said last week that it had reprogrammed software on its 737 MAX passenger jet to prevent erroneous data from triggering an anti-stall system that is under mounting scrutiny following the two deadly nose-down crashes. The world’s largest planemaker said the anti-stall system, which is believed to have repeatedly forced the nose lower in at least one of the accidents, in Indonesia last October, would only do so one time after sensing a problem, giving pilots more control.

It would also be disabled if two airflow sensors that measure the "angle of attack," or angle of the wing to the airflow, a fundamental parameter of flight, offer widely different readings, Boeing said last week. (Reporting by David Shepardson Editing by G Crosse and Sonya Hepinstall)