GP: Oscar Munoz, chief executive officer of United Continental Holdings Inc., speaks during a Bloomberg Television interview in Chicago, Illinois, U.S., on Wednesday, April 24, 2019.

United Airlines CEO Oscar Munoz said Wednesday that he has no idea when Boeing's grounded 737 Max jets will fly again.

"I think it's fair to say that we do not know yet ... We have really no sense of it at this point in time," he said on CNBC's "The Exchange."

The Max has been grounded since mid-March after its anti-stall software was implicated in crashes in Ethiopia and Indonesia since October that killed a total of 346 people. United has grounded its 14 Boeing Max jets through early July, along with other carriers like Southwest and American.