We’ve heard of musicians having trouble flying with their instruments as carry-on items in the past, but American Airlines is apologizing to a man who bought a seat for his cello, only to be told he had to leave the flight because it was a “safety risk.”

The man was sitting in his seat for a flight from Washington, D.C., to Chicago on Tuesday with his cello placed in its paid-for neighboring seat, when he says a flight attendant and a pilot asked him to leave, telling him the cello wasn’t allowed on the aircraft, reports WJLA.com.

“Either I could voluntarily leave, or I could be removed from the airplane,” he told WJLA, adding that he was “mortified.”

He says the crew pointed to a manual that said bass fiddles aren’t allowed on their plane. Although he tried to explain that the instrument was actually a cello and not a bass, the pilot told him his mind was made up. He says he was told it wasn’t approved for flight because the cello would graze the floor as it wasn’t strapped in, thus posing “a safety risk.”

He asked for a seatbelt extender to help keep the cello in place, but says he was denied. He says he’s flown with his cello at least 40 times in the last three years, but the last time he can remember having a problem was 12 years ago

“Before humiliating a passenger in front of 150 people, for no reason whatsoever, they should know what a cello is, and what is really approved to be in flight,” he said.

He says a ground agent told him there had been a mistake and apologized on behalf of the airline. He and his cello were booked on the next flight to Chicago.

American now says it’s looking into what happened and has apologized to the musician for “any inconvenience he experienced.” The airline notes that musical instruments like cellos are allowed on planes, as long as they meet seat size restrictions and weigh no more than 165 pounds. American has refunded the $150 the musician paid for his cello’s seat.

The musician hopes American will learn from this, and better train its staff so others don’t have to go through what he did.

Last year, American found itself apologizing after refusing to allow a concert musician to board a flight carrying her 18th-century violin, despite the airline’s policy that says small musical instruments can be treated as a traveler’s carry-on.