I'm going to take an optimistic stance and predict that a safe and reliable vaccine will be available within the next year. However, even with a good vaccine it will take months to treat a large enough portion of the world's population for things to return to "normal". Therefore, patience and diligence will be required by all, because there are no short cuts out of this pandemic-constructed maze.
However, airlines will be facing some tough long-term planning decisions:
For the US "Big 3", they will need to grapple with multiple issues: 1) Do they have too many hubs? 2) Fleet simplification (while still dealing with the impact of the B737MAX fiasco). 3) Future relationships with their regional partners, especially as it pertains to 50-seat jet flying (do they still need this feed?). 4) Inflexible work rules that currently limit productivity. 5) How much international flying is needed and to where? 6) How do they service all that debt they took on when business was booming?
1) They don't have too many hubs at this time. Hubs allow the US3 to dominate flying from a metro area.
That may change if the major companies in a metro area reduce travel more than say 2/3
2) Each of the US 3 was handling fleet simplification in their own way. COVID actually makes that easier since there are large redundancies in aircraft. Unless you are AA and most of your aircraft are new and mortgaged.
3) There will be blood regarding the regional partners. Has already started (with Expressjet). But 50 seat flying, while it may shrink, will not disappear anytime soon. There are markets that will pay the 50 seat cost.
4) I don't understand what work rules are limiting productivity other than scope clauses. Which for the most part, are legitimate efforts to keep airlines from flying more than half of their flights with regionals
5) International flying is the big question. For the most part, the US3 fly to major city pairs that will survive if anything international survives. But will international flying survive? Or will the US3 have to dump most of it to conserve cash? Significant question that deserves its own thread.
6) DL and UA have been paying down debt since 2008. WN never had a whole lot of debt. The only one with significant debt issues is AA. Which has its own thread already.