Airlines themselves are perfectly fine. It's relatively hard to break into as a disruptor, but the employees of the established players are mostly well-paid. The executives are even better-paid. The investors can earn steady, predictable, positive returns as long as the stock is reasonably priced and doesn't make assumptions about impossible levels of future growth. Airlines are not super-profitable, but with sufficient volume, you don't need high margins, and they're at least profitable as long as we don't have 9/11 or Covid happening.

I'm not personally knowledgeable about this or anything, so look into it yourself, but just picking a random really big one, United Airlines, it looks like they consistently beat the S&P 500 for most of the past 20 years, until Covid, and the past four years since then have been pretty bad.