The Federal Aviation Administration will delay certification of Boeing’s latest 737 MAX model as air-safety regulators assess a new software glitch that some industry officials worry may pose a potential safety risk while landing, the agency chief said Monday. Boeing has been seeking to win the FAA’s approval for the MAX 10, the longest version of the 737 variant.

“We haven’t concluded whether this is a safety-of-flight issue or not,” FAA Administrator Bryan Bedford said at a press conference Monday. “But we will be delaying the 10 until we’re satisfied that we don’t have an issue here.” The FAA hasn’t telegraphed publicly when it had been planning to certify the aircraft, but industry and government officials have said regulators were expected to approve the 737 MAX 10 for passenger service as soon as October.

For Boeing, a safety setback could damage its efforts to restore trust after its 737 MAX was grounded for nearly two years after a pair of fatal crashes. Boeing’s stock fell 6.9% Monday, its largest single-day drop since April 2025. The FAA in August certified the smallest variant, the 737 MAX 7, with the software bug, and Bedford said those planes were safe.

The glitch, which Boeing acknowledged, emerged from a cockpit software update developed by GE Aerospace. Bedford said such updates often try to fix various issues, adding, “Is that weeks, days, months? It remains to be seen.”