On aircraft, vertical stabilizers generally point upwards. These are also known as the vertical tail, and are part of an aircraft's empennage. The trailing end of the stabilizer is typically movable, and called the rudder; this allows the aircraft pilot to control yaw.
Often navigational radio or airband transceiver antennas are placed on or inside the vertical tail. In most aircraft with three jet engines, the vertical stabilizer houses the central engine or engine inlet duct, as in the Lockheed L-1011, McDonnell Douglas DC-10, McDonnell Douglas MD-11, Boeing 727, BAe Trident, Tupolev Tu-154, and the Yakovlev Yak-40.
T-tails are often incorporated on configurations with fuselage mounted engines to keep the tail away from the engine exhaust plume.
T-tail aircraft are more susceptible to pitch-up at high angles of attack. This pitch-up results from a reduction in the horizontal tail's lifting capability as it passes through the wake of the wing at moderate angles of attack.
T-tails present structural challenges since the horizontal tail loads must be transmitted through the vertical tail.
Rather than a single vertical stabilizer, a twin tail has two. These are vertically arranged, and intersect or are mounted to the ends of the horizontal stabilizer. The Beechcraft Model 18 and many modern military aircraft such as the American F-14, F-15(left), and F-18 use this configuration. The F-18 and F-22 Raptor have tailfins that are canted outward, to the point that they have some authority as horizontal control surfaces, both aircraft are designed to deflect their rudders inward during takeoff to increase pitching moment.
A variation on the twin tail, it has three vertical stabilizers. The best example of this configuration is the Lockheed Constellation. On the Constellation it was done to give the airplane maximum vertical stabilizer area, but keep the overall height low enough so that it could fit into maintenance hangars.