I took Ryanair for MAD-STN and STN-MAD and had no problems either way. There is no bright, clear sign leading non-EU people to the right place to get their documents checked, so this is a bit of a nuisance to figure out. Also, I made the luggage requirements for checked and hand luggage, but I underestimated how much having a laptop and peripherals and overdoing the hardcover books this time would make that more difficult.