And leaders of unions that represent flight attendants are reacting with outrage.

American, United and Delta all indicated Thursday that they will lift the bans they imposed now that masks are optional on flights.

"We have talked to them individually," United CEO Scott Kirby told NBC. "Many of them assure us that now that the mask mandate is off, everything is going to be fine, and I trust that the vast majority of them will."

American Airlines Chief Government Affairs Officer Nate Gatten told reporters that "in most cases," people who were banned over masks will be allowed back, but that won't extend to the worst offenders.

"In cases where an incident may have started with face mask non-compliance and escalated into anything involving something more serious — certainly an assault on one of our team members or customers — those passengers ... will never be allowed to travel with us again," Gatten said.