In spite of the potential cost difference, you might want to wait to know your student’s schedule. Often kids are finished before the end and leave days earlier accordingly. You could be missing out on 2 - 3 days more time together. Flights on Southwest to BWI tend to run around $100 even at normal times as long as you purchase them at least three weeks in advance. I always made my guy’s flight arrangement as soon as I knew his schedule. Now that he’s an RA I know he needs to stay until the end, but RAs also stay some days on breaks, so I still need to wait to see what his days are…