Do yourself a favor and leave earlier and try to get to the airport by 430pm
if that's possible. The Baltimore beltway isn't as bad as DC's Capital Beltway, but traffic is a pain and [B]a single accident on 695, 95, or 295 (BW Pkway) can make life miserable, especially during rush hour.
[/B]
The poster just ahead of me nailed it when he said the first 2/3rds of the trip is a piece of cake.The last 1/3 can be problematic.

I'd go early, and find a place for an early dinner or snack somewhere in or near the airport.