Delta Air Lines Inc. Chief Executive Officer Ed Bastian said he was “appalled” to hear insulting remarks about U.S. flight attendants by his counterpart at Qatar Airways Ltd.

Qatar Airways CEO Akbar Al Baker disparaged U.S. flight attendants as “grandmothers,” while boasting that his airline’s cabin crews had an average age of 26. He apologized on Wednesday after a firestorm of criticism from labor unions and American Airlines Group Inc., the carrier in which Al Baker is interested in buying a major stake.

“I was appalled to hear Akbar’s comments about our people,” Bastian said on an earnings conference call Thursday. “I’m told he has apologized, but I think that’s woefully inadequate. There’s a consistent theme there that he wants to skirt the rules and play by his own rules.”

Delta, American and United Continental Holdings Inc. have pushed the U.S. for two years to open talks on whether Qatar Airways, Emirates and Etihad Airways PJSC use government subsidies to compete unfairly. The dispute has sparked rounds of verbal sparring, with Al Baker often criticizing the quality performance of the U.S. companies.

Bastian said he was glad that Delta employees and those at other U.S. airlines “spoke with one large voice to say that it’s unacceptable, inappropriate.”

Al Baker said he won’t be discouraged from investing in American despite the Fort Worth, Texas-based carrier’s decision to end marketing agreements with Qatar Airways and Etihad as of March 24.

“Once we get the OK from the regulator, we will buy the stock that we said we are going to buy,” Al Baker said.