A RARE warning has been issued by federal regulators that could affect travelers.

The warning regards Boeing 737 MAX engines that could malfunction, letting smoke into an airplane cabin or cockpit.

A malfunction can occur if the engine’s oil system is damaged, causing smoke from the hot oil to enter the plane’s ventilation system.

If smoke fills the cabin or cockpit, it can possibly incapacitate pilots, said the National Transportation Safety Board in a report.

Following two bird strike incidents on Southwest Airlines flights, where CFM International LEAP-1B engines failed and cabins filled with smoke, a warning was issued.

The other incident happened in December 2023, when a Boeing 737-8 filled with “acrid white smoke” right after takeoff from New Orleans.

The smoke was so thick that the captain had issues seeing the instrument panel, according to the NTSB.

Earlier in the year, in March 2023, a similar situation occurred when an engine on a different flight sustained damage from a bird strike, leading to fog entering the cabin just after departure from Havana, Cuba.

Both flights resulted in emergency landings with no reported injuries, said the NTSB.

The agency is recommending modifications to the engines, which are used on Boeing MAX 737 planes and Airbus A32 jets.

The notice calls on the Federal Aviation Administration to evaluate whether the LEAP-1A and LEAP-1C engines could have the same issues.

“We advised operators to evaluate their procedures and crew training to ensure they address this potential issue,” the FAA said in a statement.

“When the engine manufacturer develops a permanent mitigation, we will require operators to implement it within an appropriate timeframe.”

The NTSB was also worried about flight crews being unaware of the possible smoke hazard, leaving them unclear about what to do in an emergency.

The agency urged the FAA to require companies such as Boeing to alert crews of the potential risk.

The FAA stated, “This includes reviewing procedures and crew training to make sure they effectively address this issue, and assessing if training simulators are showing the correct response to an engine failure that activates the Load Reduction Device.”

The agency added that once the engine manufacturer “develops a permanent mitigation,” the FFA will require operators to add the change “within an appropriate timeframe.”

Boeing said it had already changed its flight manuals for these situations, said the NTSB.

“CFM International and Boeing have been working on a software design update. We support the NTSB’s recommendation,” Boeing told The New York Post.

GE Aerospace told CNN that it also made changes.

“We are aligned with the NTSB’s recommendations and the work is already underway, in close partnership with our airframers, to enhance the capability of this important system,” the company said in a statement.

The U.S. Sun has reached out to Boeing and the NTSB for comment.