He might be getting just too friendly in the skies.

The CEO of United Airlines was caught flying first class with rival American Airlines, his old employer who he has repeatedly taken jabs at and even pitched a merger to after they let him go a decade ago.

Scott Kirby, 58, was seen on an American Airlines flight from the San Francisco International Airport on Friday, with flight attendant Kristine Tiley snapping a photo with her former boss.

“LOOK WHO I HAD IN my first class today from sfo. What a great guy,” Tiley wrote on Facebook. “Just as nice as he was back in the day He misses us lol. And tells everyone Hi.” 

The post whipped social media up into a frenzy as many were confused as to why the chief of United Airlines would fly with American rather than with his own company.

Kirby still enjoys lifetime travel benefits with American Airlines after serving three years as president of the company from 2013 to 2016.

In his final year, American Airlines let Kirby go, paving the way for his rival, Robert Isom, to move up to CEO of the company, with the two men becoming heated adversaries in the industry.

Thanks to his contract, Kirby was able to immediately work for a competitor, with the businessman settling at United — where he helped pushed the airline to success while constantly taking jabs at his old workplace and nemesis.

Kirby has most recently been trying to push for the two airlines to merge together, even pitching the idea directly to President Trump during a February meeting, sources told Reuters.

The United CEO eventually confirmed last month that he had been seeking a merger, but that Isom and American were not interested.

“I was confident that this combination, which would have been about adding and not subtracting, creating a truly great airline that customers love, could get regulatory approval,” Kirby said in a statement.  “I was hoping to pitch that story to American, but they declined to engage and instead responded by publicly closing the door.”

With American rejecting the proposal, Kirby said he was ending his months-long pursuit to merge with the competitor.

United Airlines did not immediately respond to The Post’s request for comment.