WASHINGTON D.C. — A crucial fire-fighting system on Boeing's fleet of 787 Dreamliners was found to have the potential to malfunction, sparking fears among airline pilots.

The Guardian reports that Boeing warned airlines using the 787 Dreamliner that the switch used to extinguish engine fires has failed in a 'small number' of instances.

According to Boeing's airline alert, long-term heating can cause the fire switch to remain locked so it can't be used to release the two extinguishers in each engine.

Boeing claims the risk of fires is low. But a pilot told The Observer that should the switch malfunction during an engine fire, there's no manual override to deploy the extinguishers, and therefore no way of putting the fire out.

The Federal Aviation Administration admitted the malfunction is a risk to the flying public, but decided not to ground the fleet. Instead, it issued an airworthiness directive and required airlines to inspect the switches every 30 days.

According to the Observer, the pilot community says Boeing's attitude to the risk is upsetting, especially in light of recent issues with the 737 Max.

The FAA has declined to comment on the pilots' concerns, saying only that it invited feedback from the airline industry back when its directive was proposed in February.