There’s no federal mask mandate. All U.S. airlines require passengers to wear masks. So most people assume that the only penalties for non-compliance are imposed by airlines. That’s not true.
Airlines only impose penalties, other than asking a passenger not to fly, when enforcing mask rules leads to an altercation. But when an altercation occurs, the FAA can impose penalties too. In other words, you don’t need a federal mask mandate to punish passengers for bad behavior.