What was "normal" in 2019 / early 2020 will never be normal again.
Health checks at airports may remain in place for many years or permanently.
Something similar to the yellow fever vaccination and card my be needed for COVID

Aircraft loads will take may years to build back up to the levels of early 2020.

Businesses have learnt that meetings do not have to be held face to face - this means the demand for business travel will not quickly recover. As a consequence airlines will have excess capacity. the airlines have two options
decrease supply - fly less often often with smaller more economical planes
increase demand - Make their airline the one people chose (better bus class product, better FF schemes etc)
I don't think this will happen, but remember the peak of FF schemes and bus class product was when airlines had excess capacity and wanted to fill seats. These have both been reduced as carries fly with high loads.

More airlines and hotel chains will go bankrupt before the COVID situation recovers
This could mean mergers or even just the outright closure of these businesses.

Governments will go into massive debt trying to support their failing economies.
When the COVID situation is over, COVID recovery taxes will be introduced to cover this debt.

I don't think the airline and travel industry will ever be what is was before.
There will be no recovery of the airline industry if there is no vaccine and borders are not reopened.

But that's enough optimism for one day