You have to be at the airport so early traffic will not be a major concern, the driving part should take about 30 minutes or so, but parking and getting to the terminal will be time consuming. I would allow at least 30-45 minutes for that alone. Economy parking at the airport has just gone up to $12 a day at the airport. I always park at a Crystal City hotel and take their shuttle to the airport. The cost usually runs anywhere from $6-$10 per day. You can google DCA airport parking and many options will come up. Just an FYI - if you are considering Super Shuttle, they are not allowed on the base. I volunteer for Travelers Aid at National Airport and found this out last week when I was assisting someone with transportation to the base.