BWI is another good airport for planespotting. There is actually an Observation Gallery inside the main terminal, between the “B” and “C” concourses and offers a good view of the “B” and “C” gates (Southwest and Delta) along with a radio system that has a continuous feed of the tower, ramp, and approach frequencies. The gallery is before the security checkpoint so it is open to anyone, even those not flying. If you are flying and want to go to the gallery between flights you’ll have to check through security again to return to your gate so plan for the extra time. If you are not arriving on a flight you would have to pay the parking garage hourly fee to park and visit the gallery. Here is a picture of the inside of the observation gallery:
Outside the airport there is a park across the street from the end of runway 15R/33L. It is called Thomas Dixon Aircraft Observation Area, or Friendship Park. There are some walking trails, kids play area, and covered gazebo with benches. This runway is the one used most often and if planes are landing to the north (15R) they will pass over this park quite low. You cannot see the actual runway though. Some traffic may use the east-west runway and you cannot see those aircraft either. The park is free, safe, and clean. To get there just exit I-195 in Baltimore at Aviation Blvd south, go to Dorsey Rd and make a left, and then go about two miles.
Here is an example of a photo taken from Friendship Park:
Most traffic here is Southwest Airlines (145 flights/day) but there is a good mix of all the other major airlines too. There are even some international flights and widebody jets. Since Baltimore is only a half hour drive from the D.C. area, you can combine a visit here with a visit to the Dulles and Reagan National airports which also have great viewing opportunities.