Actually flights are selling out - I already booked mine but have been watching the site of the airline I use, the number of flights we can take are getting smaller and smaller lol. My cousin is also flying in (different airline, different location) and now has to go the day before she was planning since the flights the day she wanted was all sold out. You'll be surprised I think. What I think you're seeing is that many aren't staying downtown. They're staying outside DC and plan on commuting in.