Bargain-hunting higher flyers might, while planning their next adventures, come across airfares that are so good that they’re too good. Budget airlines like Spirit and Frontier (in)famously offer such cheap prices, but they also inundate their customers with fees in order to generate additional revenue. That’s to be expected, but sometimes you’ll see legacy carriers like American, Delta, and United selling flights at prices comparable to those low-cost rivals. While such deals might look particularly enticing — especially when you consider that these three have better reputations than Spirit — you have to be wary of the catch(es). These discounted tickets, known as basic economy fares, are heavily restricted and can seriously hurt your ability to fly higher. But but but! If you know what you’re getting in to, they can also represent outstanding values.