I am doing this in February. We are flying out of Detroit on Southwest and returning on Spirit Airlines. I HATE layovers. Southwest doesn't go non-stop from Detroit, so I took the only flight that didn't require a plane change. I had a credit of $400 to use on SW, so I decided to go for it. I didn't like any of the return flights on SW, so I decided to book the return on Spirit, which is a non-stop flight. I've never done this before, but I'm not worried about it. They may spend more time screening us, but it's not like we are purchasing these one way tickets in cash at the counter. I can show them our return tickets if they want to see them. I have high hopes that it won't be a problem.