Or the earth could be wiped out by a meteor, or a super volcano eruption. There are a ton of unknowns, hindsight is always 20/20, but foresight never is. We have to make rational decisions based on available data and likely probabilities. I'm closer to the end of my career than to the start of my career. However, if I was deciding at this point in time, I'd pick United over Southwest based on forecast seniority growth. I'd also pick United over Southwest because I prefer having variety in my career, domestic and international, narrow body and wide body. Personally, I prefer the culture of United to that of Southwest, but some people may prefer the culture over there.