The Unusual Reason that United Airlines Was Forced to Ground A321neo Fleet

United Airlines this week was forced to ground its fleet of new Airbus A321neo planes because of a little-known 1990 law.

United, which has five of the planes in its fleet, started operating the A321neo in December 2023. All five of the planes were dropped from United’s schedule earlier this week because of how the “No Smoking” signs operate, or don’t operate, onboard.

Unlike older models, the A321neo is designed to keep the “No Smoking” signs on continuously during the flight, not allowing the flight crew to turn it off and on manually. That 1990 law, which is known as “‘US code 14 CFR § 121.317(a),” requires all planes to give flight crews the ability to turn the signs on and off while flights are operating, even though smoking has been banned on flights since 2000.

United, and other carriers, have an exemption for that law with the Department of Transportation (DOT) for most of its fleet, including all of its Boeing planes, which have “No Smoking” signs designed to stay on at all times

However, United did not apply for an exemption to that law for its new A321neo fleet, which prompted the DOT to ground the planes this week.

Shortly after the groundings, United requested an exemption for the A321neos. It wrote in a letter to the DOT that the design, despite it violating that 1990 law, produces “no adverse effects to public safety.” It added that the way the “No Smoking” signs are set up on the new planes is actually in the “best interest of the flying public.”

“United’s fleet configuration of “No Smoking” signs being continuously illuminated without flight crew ability to turn them on and off is in the best interest of the flying public because it increases the level of safety by preventing a ‘No Smoking’ sign from being inadvertently turned off,” United wrote to the DOT.

The FAA, shortly after, said it would allow United to operate the planes, avoiding any further disruptions to it schedule, as it reviews the request for an exemption. The planes were out of service for only a day, and United said that it had worked through its schedule to avoid any cancellations and only a few delays following the groundings.