I think the most salient point about travel I've learned in the last 6 months or so is that pretty much all of it is discretionary. I guess I always knew that, certainly for tourist travel, but the gamechanger is how quickly business travel has become a distant memory for most (both domestic and international).
With tourism you'll always get the desperate dan's who'll jump through fire for that 2 weeks in the Sun, but I doubt that will drive much above the 25-30% capacity mentioned above. Anything more than that relies on "normality" being restored, i.e. a vaccine. Even if a vaccine is released I'd expect it will be too late to fend off some pretty deep recessions in many traditional tourist markets, that in itself will further suppress demand for discretionary travel, be it stag do's in Krakow, weekends away in Nice, bucket and spade to the Med, etc. Once those economic side effects subside then yes I do expect tourist travel to pick up significantly, but this could be 4-5 years away to get back to pre-Covid levels.
For business I'd say the outlook is even more uncertain, and potentially gloomier. My experience is that many businesses are finding (1) they are getting by perfectly fine with Zoom, Teams et al and (2) the cost savings generated from the 100% reduction in travel are huge. I honestly see very little incentive for big business to get back to normality anytime soon, or even ever. I'd expect a very gradual uplift in business travel as restrictions are eased, but with a very low likelihood of overall business travel ever returning to pre-Covid levels.
Therefore the challenge for the major airlines is to accept the new normal (at least for the next few years) and to adapt to survive, and principally this is all about cutting capacity and costs to a point where they support demand. As is often the case I suspect those that take tough decisions soonest will be best placed to survive and prosper in the long term, and those that do too little too late wont be around much longer.