Boeing Wants FAA to Clear Smallest 737 Max Jet Despite Overheating Problem

Boeing is asking U.S. aviation regulators to certify its smallest 737 MAX aircraft by exempting it from a safety rule issued last year related to the engine anti-ice systems on newer 737s.

In August, the Federal Aviation Administration issued an airworthiness directive for operating the 737 MAX anti-ice system because using it for more than five minutes in dry air at certain altitudes, temperatures and thrust settings can cause overheating on some parts within the engine covering, known as a nacelle.

The risk is that high temperatures can cause parts of the engine’s inner barrel to break off in an uncontained manner and exit the nacelle, potentially piercing windows or other parts of the fuselage behind the wing. 

In its November petition, Boeing said the MAX 8 and 9 variants have accumulated over 6.5 million flight hours since 2017, with no reports of engine parts breaking free due to overheating and that an exemption for the smallest MAX 7 will have no “adverse effect on safety.”

The FAA can’t certify the MAX 7 without granting Boeing an exemption for the anti-icing system. Boeing wants the exemption through May 31, 2026, and says it is designing a long-term solution that will be retrofitted to the entire MAX fleet. 

“Under established procedures, we requested to certify the 737-7 with the same inlet design and engine anti-ice system that is used across the entire 737 MAX fleet,” a Boeing spokeswoman said Friday in a statement. Pilots would continue using existing measures to prevent potential overheating that could occur “under very specific weather and operational conditions.”

Southwest Airlines is keen to begin flying the smaller airplane in late 2024 after years of delays from two fatal crashes that led to a prolonged grounding of Boeing’s newest 737 models. Aviation regulators ordered the MAX grounded in March 2019 after two of the new jets crashed, in Indonesia and Ethiopia, killing 346 people. MAX flights in the U.S. resumed Dec. 30, 2020.

The 737 MAX family consists of four models, ranging in size from the -7 to the -10. The -8 and -9 are already in service with numerous airlines worldwide, including American, Southwest, United, Alaska, Singapore and Ryanair, which flies a slightly longer -8 version, with more seats.

The FAA published Boeing’s request Dec. 4 in the Federal Register, seeking public comments.

The Foundation for Aviation Safety, a nonprofit lobbying group founded by a former Boeing 737 manager, Ed Pierson, filed comments Dec. 24 opposing the exemption request.

“The flying public would be exposed to a potentially catastrophic failure resulting from the flight crew inadvertently forgetting to shut off the cowl anti ice system on both engines,” the group said. “There is no ‘caution’ or ‘warning’ annunciation to the flight crew when they are operating the anti-ice system in flight conditions where catastrophic damage to both engines will occur.”

The three largest U.S. pilots unions — which represents pilots at U.S. 737 MAX operators American, Southwest, Alaska and United — did not file comments on the exemption request. Southwest is the only U.S. airline with public orders for the smallest MAX. It did not comment on Boeing’s exemption request, nor did other airlines.

“We don’t have a role in the certification process and we’ll follow the direction of the FAA,” Southwest spokesman Chris Perry said in an email. Southwest changed its flight manual so that pilots follow FAA direction on how to operate the anti-ice system safely, he said.

“Boeing is talking about getting a fix in 2026. That’s way too long for such an impactful issue,” said Dennis Tajer, a spokesman for the Allied Pilots Association, which represents American Airlines pilots, and a 737 MAX captain based in Chicago.

FlightGlobal first reported Boeing’s request for an exemption of the system.