VTOL stands for Vertical Take-Off and Landing, referring to aerial craft that can take off and land vertically, without the use of a runway. Few aircraft are truly VTOL. Those that do exist are relatively expensive, but invaluable for certain applications, such as quick getaways for Special Ops teams. The first practical VTOL was the Hawker Siddeley Harrier, introduced in 1969. It was one of several successes among numerous failed efforts to develop VTOL craft that were pursued in the 60s.
The motivation behind creating a VTOL is to produce a craft capable of vertical takeoff, like a helicopter, while retaining the desirable features of fixed-wing aircraft, such as high cruise speeds. Indeed, the VTOL-equipped French Dassault Mirage IIIV achieved speeds of Mach 1.32 during testing.
VTOL craft tend to be expensive, hard to design, and sometimes dangerous. For example, the V-22 Osprey, the VTOL craft of choice for the United States Marine Corps, costs about $130 million US Dollars (USD). Three have been lost during testing, killing everyone on board in every case. As of 2005, a study concluded that the V-22 Osprey, whose development program cost $30 billion USD, is now sufficiently mature to serve as a reliable and safe craft for the military. The V-22 Osprey utilizes a tiltrotor design, allowing it to take off like a helicopter, but tilt its rotors forward during horiztonal flight, turning them into propellers.
Early ideas for VTOL craft involved using curved ducts to direct thrust towards the ground, but implementing this is much harder than it seemed at the time. A case is point is the V-22 Osprey, which skips this approach and goes for rotors.
There are two quite famous VTOL craft: the Harrier Jump Jet, and the Apollo Lunar Module used by astronauts to take off from the Moon after they were done with their visit. "Harrier Jump Jet" refers to all craft in the Harrier family, the first example appearing in 1969, with several modern versions featuring complete redesigns. The Jump Jet is used by the military both the United States and Great Britain.
The Moller Skycar, a prototype flier whose builders say will be the first affordable skycar for the masses, utilizes VTOL. However, as of this writing, it has not been flown horizontally with people in it yet. Reservations for Moller Skycars are available for a cost of $500,000 USD.
