A dead fetus was found in a bathroom toilet of a commercial plane at LaGuardia Airport on Tuesday morning, police sources told The Post.

The gruesome discovery was made around 7:30 a.m. aboard an out-of-service American Airlines flight at Hangar 5, the sources said.

A cleaning crew found the fetus in the bathroom of the plane, which had landed in New York on Monday night from Charlotte, North Carolina, according to a high-ranking police source.

The fetus was between three to six months along.

American Airlines Flight 1942 departed from Charlotte Douglas International Airport at 9:08 p.m. Monday and arrived in Queens about 90 minutes later, according to records on FlightAware.com. It was the Airbus A321’s only flight of the day.

The City Medical Examiner is working on determining how the fetus died.

“The OCME can confirm we’re investigating what we believe to be a human fetus found deceased on an airplane,” the agency said.

Just before 9 a.m., the airport tweeted about possible delays over the incident.

“American Airlines flights at Terminal B may experience some delays due to an out of service aircraft. Please check with @AmericanAir before your departure,” the post said.

But a spokesman for the airline said, “We have no major impact to our operation this morning while we are working with law enforcement on an investigation.”

The airline later said in a statement: “As we continue to learn more about this tragic and sensitive situation, we are actively cooperating with law enforcement in its investigation.”

The Port Authority deferred questions to the Queens DA’s Office, which said it was looking into the matter.

A traveler who was scheduled to fly out of LaGuardia to Charlotte at 7:55 a.m. was frustrated that her flight was delayed three times without explanation.

“They didn’t tell us anything until we were already waiting at the gate,” she griped. “We didn’t find out until about 7:40 a.m. that the flight was going to be delayed.”

Additional reporting by Stephanie Pagones and Georgett Roberts