This is certainly possible.
Especially if you consider that even if demand recovers to 2019 levels, the airline companies will be in a worse position a they will have much more debt than they had in 2019 (or dilution to shareholders).
No one on here can give you advice, just their opinion.
Also, the risk of the investment will also depend on how much of your portfolio you allocate. If you are investing 10% of your portfolio into airline stocks, my initial thought would be that it is very risky, however if you are only allocating 5% of your portfolio then that seems much more manageable. In my view the total number doesn’t matter as much, it’s to do with the overall weighting within your portfolio and how that affects your risk exposure. I would not be comfortable having 90% of my portfolio invested in only “re-opening and recovery related stocks” such as airlines, cruisers, restaurants, hotels and oil, it would be too concentrated. My opinion is that it is important to be diversified. If everything goes well and demand soars in 2021, 2022, etc as people want to travel and catch up on all the missed travelling then airlines could do very well though.
Also, if for whatever reason we get a new covid variant that is not affected by the vaccine and countries have to close again, that could be the end of many companies.
One other interesting factor, open to discussion is, how do we think the aviation sector will be affected by the number of planes that companies disposed of in 2020?
If plane flights recover to 2019 levels, the reduction in the size of plane fleets could lead to increased prices as the supply if planes/flights is lower than it was in 2019. Having said this, @topher 's point on business flights is very true, I imagine that companies will reduce the number of flights they ask their employees to take to much lower levels than before the pandemic. I think it is currently unclear if that demand will ever recover.