Boeing may have to replace the locks on 2,600 aircraft after a passenger was locked in an airplane toilet. The cost could be over $3 million, according to a report. Business Insider.

It was early last year that a passenger on a flight between Mumbai and Bangalore in India became involuntarily locked in the aircraft toilet. The broken locking device meant that even the flight crew was unable to open the door. The situation was seen as a safety risk and the pilot was forced to make an emergency landing.

The US Federal Aviation Administration (FAA) has now investigated the incident and concluded that the locking device in question on all aircraft needs to be replaced. This concerns a total of 2,600 Boeing 737 planes.

The lock replacement directive is being issued because a passenger locked in a toilet could be at high risk of injury in the event of severe turbulence or a medical emergency, the FAA said, according to Business Insider.

The agency estimates that the lock replacements will cost around $3.4 million, or 33 million kronor.