48. A typical ultralight aircraft (with pilot on board) weighs about 400 lb, has a wingspan of 28 ft, and has a maximum speed of 65 mph. Also, solar and human-powered aircraft, such as the Gossamer Condor and other superlightweight planes, fly more slowly than Example 10 (page 756) predicts; for instance, the Gossamer Condor is far longer than an ostrich, but it flies at only 12 mph. How are these aircraft possible?