President Joe Biden made a joke about Boeing during a campaign reception on Thursday in New York.

During a discussion at the reception with Biden and former Presidents Bill Clinton and Barack Obama, talk show host and moderator Stephen Colbert posed a question about the three men’s experiences riding on Air Force One, the Boeing jet that presidents usually fly on.

“All three of you have been on Air Force One. You still have the keys, Mr. Biden. That’s made by Boeing, right? Do those doors stay on? Before you get on, do you send [over] Pete Buttigieg with a socket wrench set to tighten them?” Colbert asked.

In response, Biden quipped: “I don’t sit by the door.”

As the audience laughed and applauded, he continued, “Obviously, I’m only kidding. And I shouldn’t even joke about it. I shouldn’t even joke.”

“A fine American company,” Colbert responded.

A spokesperson for Boeing declined to comment on the joke.

Boeing has been subject of scrutiny and investigation after a rash of safety incidents. On Jan. 5, a door-plug panel blew off an Alaska Airlines Boeing 737 Max just seven minutes after takeoff, leaving a gaping hole in the side of the plane and forcing pilots to make an emergency landing.

According to investigators, four bolts that were supposed to secure the door were missing after the plane was worked on at a Boeing factory in Washington.

In a preliminary report in February, the National Transportation Safety Board said that the bolts were missing after the panel was removed so contractors could fix damaged rivets nearby last September.

Jennifer Homendy, chair of the NTSB, testified in a Senate committee hearing in March that Boeing had refused to identify the employees that worked on Boeing 737 door panels and didn’t provide documentation about the repair jobs done in September.

Boeing maintained that it had given employees’ names to the NTSB and had previously identified some of them to investigators.

The Department of Justice launched a criminal investigation this month into the Jan. 5 incident to determine whether Boeing was in compliance with a previous settlement that resolved a probe into the safety of its 737 Max aircraft, after two 737 Max 9 crashes in 2018 and 2019.