Boeing's New MAX Nav Software Rejected by Southwest and United

Two major US airlines, Southwest and United Airlines, have asked Boeing to deliver incoming 737 MAX jets with an earlier software version, skipping the newer flight-management software tied to a navigation glitch under federal investigation.

The issue affects versions U.14 and U.14.1 of the affected software, which can cause the automated vertical-navigation function (VNAV) to disengage during a specific sequence of events: when a crew abandons a landing, initiates a go-around, then modifies the aircraft's preprogrammed route for another approach.

Without VNAV, pilots must manage altitude and descent guidance manually, adding workload during a low-altitude phase of flight that already demands close attention. Boeing says existing procedures allow crews to handle the situation safely and that pilots are trained to land without automated VNAV.

The airlines' request is not a safety declaration but rather a configuration preference while regulators work through the implications. The FAA has opened a Corrective Action Review Board to evaluate the issue, and Boeing has shared its findings with the agency.