The McDonnell Douglas F-4 Phantom II is a tandem, two-seat, twin-engine, all-weather, long-range supersonic jet interceptor fighter/fighter-bomber originally developed for the United States Navy. Its thin-section wing had a leading edge sweep of 45-degree and was equipped with a boundary layer control system for better low-speed handling. Wind tunnel testing had revealed lateral instability requiring the addition of 5-degree dihedral to the wings. To avoid redesigning the titanium central section of the aircraft, McDonnell engineers angled up only the outer portions of the wings by 12-degree, which averaged to the required 5-degree over the entire wingspan. The wings also received the distinctive "dogtooth" for improved control at high angles of attack. The all-moving tailplane was given 23-degree of anhedral to improve control at high angles of attack while still keeping the tailplane clear of the engine exhaust.(Wikipedia)