American Airlines and United Continental have asked the federal government not to fly immigrant children separated from their families on their aircraft as part of the Trump administration’s recent “zero tolerance” changes to border enforcement policy.

Both airlines said they had no knowledge of whether U.S. officials have used their flights to transport the children. “We would be extremely disappointed to learn that is the case,” American said in a statement Wednesday. Delta Air Lines didn’t immediately respond to a request seeking comment.

“Based on our serious concerns about this policy and how it’s in deep conflict with our company’s values, we have contacted federal officials to inform them that they should not transport immigrant children on United aircraft who have been separated from their parents,” United Chief Executive Officer Oscar Munoz said in an emailed statement.

“We have no desire to be associated with separating families, or worse, to profit from it,” said American, which made a similar request of the government.

The airlines’ requests came as President Donald Trump said Wednesday that he’ll sign an executive order to halt the separation of children from their families, a practice that has drawn fierce criticism, both domestically and around the world. Pope Francis condemned the family separation policy as “immoral” and “contrary to our Catholic values.” British Prime Minister Theresa May called it “deeply disturbing” and “wrong.”

American, the world’s largest carrier, fielded media inquiries about a social media post last week relating the purported story of a flight attendant on a Miami-bound American flight that was carrying more than a dozen distressed children.

American and United have contracts to transport federal employees, as do most major U.S. airlines. The “government does not disclose information about the nature of the flights it takes or the passengers who are traveling,” American said.