To add to this, Frontier is far worse per 10,000 passengers in terms of involuntarily bumping passengers. From January to September 2022 (page 50, pdf,) their IDB rate was 2.99/10,000, nearly six times higher than the next highest airline. Even Spirit and Allegiant are far better in this respect, despite also being ultra-low-cost carriers.

I won't completely swear off Frontier, but it has to be the only reasonable option these days for me to consider it - even the other ULCCs don't have near as many issues as Frontier seems to.