United Airlines is in a difficult place financially. It is reported that they will try to get a $5Bn bond issue away next week. Goldman Sachs is on the case according to Bloomberg. Solvency cannot be taken for granted.
Boeing's CEO was recently rapped for suggesting that he expected one of the major US carriers to fail due to the C-19 crisis. Perhaps the anger directed towards him was more a case of "not in front of the children" rather than his authoritative opinion being wide of the mark in reality.
We'll have to see how things pan out. Feeling within the US is that passengers will drive rather than fly on journeys conducive to that until a vaccination programme has been completed. And stubbornly high C-19 infections in key areas such as Florida and New York could amount to a 'lost summer' for vacation travel. The market outlook for US carriers is tough. Unless they're deemed too big to fail by government.
On the plus-side, fuel prices appear set to remain relatively low in the medium term. That helps.