United grounded 5 planes because it couldn't turn off their 'No Smoking' signs, breaking a strange FAA rule

• United Airlines "briefly" grounded its Airbus A321neos due to a peculiar rule.
• It needed an exemption from requirements flight crew be able to turn off "No Smoking" signs.
• United received an exemption for Boeing jets in 2020, but ordered the A321neos a year later.

United Airlines passengers faced delays on Monday after five jets were grounded due to a peculiar rule about "No Smoking" signs, an airline spokesperson told Business Insider.

Earlier in the day, United wrote to the Department of Transportation requesting its Airbus A321neo aircraft be exempted from a requirement that flight crew be able to turn the signs on or off.