I mean, it's an airline. While the CEO might lose his bonus, it's unlikely for a bit of short selling to drive the airline out of business (and so for people to lose their jobs), so I don't think this is really a moral issue. Also, this is exactly a price discovery mechanism - the airline isn't going to be as profitable so it isn't as valuable!
You could be right, but I think the ethics on it are less neutral than that. (it's hard to say what "a bit" of short selling is -- there are feedback loops in the stock market)
Airlines provide fast connectivity between cities for people and goods, which is valuable in a disaster situation, and by shorting a stock to make a few bucks, you'd be creating unfavorable transportation economics in a disaster situation and possibly worsening supply chain constrictions. A short seller would be profiting off the hardship of others.
