Why can the planes land coming from the north?
Under certain weather conditions, planes do land from the north onto Runway 17. Planes almost always take off and land into the wind, which at Philadelphia International Airport generally come from the west, and less frequently, from the east. While it seems like a headwind would slow airplanes down, in fact the speed of the airplane isn’t important at take off; it’s the speed of the air over the wings of the airplane that is crucial. For example, if there is a 20-mile per hour (mph) headwind and the airplane is moving at 100 mph, the relative airspeed is moving at 120 mph. But if the airplane flew with the wind instead, the airspeed would only by 80 mph (The Flying Book, David Blatner, 2003).
