DCA currently allows a maximum of 48 GA
flights per day. Furthermore, the passenger and crew manifest has to be submitted to and approved by TSA
at least 24 hours in advance, and the flight has to originate (or stop off) at one of 12 designated "pre-screening" airports where the aircraft, passengers, and baggage get screened for security as they would for a commercial flight.
So while theoretically DCA
could see up to 48 GA
arrivals per day, I doubt even that limit will be approached while the current onerous security process is in place. Frankly, I'm surprised that even 5 or 10 operations per day are willing to undergo the process as opposed to simply flying to another airport nearby.