What is the best airport to fly into to see the sights in Washington DC?
BWI may turn out to be the most cost effective airport for you. www.kayak.com is an excellent tool for trip planning. I picked a week in June and found attractive round trip rates of as low as $144 on Northwest Airlines from DTW to BWI and back. BWI may not be the closest airport; but, it may turn out to be the cheapest from the Detroit area. Consider staying in Virginia, near a Metro station. The hotels will probably be less expensive and the Metro is very convenient. Go to this website to determine where you would prefer to stay: http://www.wmata.com/ You of course have the option of renting a car or taking public transportation. This decision will hinge on how much flexibility you want and how well you ambulate. Have a wonderful trip. Washington DC is an outstanding vacation destination.