A primary requirement for VTOL aircraft is a propulsion system with sufficient power to life the dead weight of the airframe and cargo. The VTOL systems are also far more mechanically complex that a simple wing and flaps. In addition, in a multi-thrust-engine aircraft, a failure of one engine during takeoff or landing would cause serious stability problems, possibly leading to a crash. These are the primary reasons why VTOL aircraft are so rare. VTOL aircraft cost more, require more maintenance, are more prone to mechanical failures, and consume more fuel than fixed-wing aircraft in similar service. The aircraft industry is highly competitive - if you don't see something flying it is because they can't build it or it cannot compete economically with what is available. VTOL aircraft fall into the latter category, which is why their development is limited primarily to the military market. The military is less sensitive to such costs, if a mission advantage is to be gained. The complexity of the systems used in the V-22 Osprey, for example, has delayed its adoption for years. Another issue with VTOL aircraft is engine noise, since most airports are built in urban areas. Aircraft are required to adhere to strict noise guidelines during operations. An aircraft takeoff, in particular, is very noisy. Those who travel by aircraft may notice a sharp decrease in engine power (e.g., sensed through the engine noise and vibration) once the aircraft has cleared the runway and has climbed a few thousand feet. This is done for noise abatement. An aircraft operates at full power during takeoff and the initial lift phase, but can power back and climb more gradually once in the air. The period of full-power operation usually lasts for less than a minute. A VTOL aircraft, on the other hand, requires a much longer period before the throttle can be eased and requires full power for both takeoff and landing, unlike a conventional fixed-wing aircraft. VTOLs are, therefore, much noisier to operate and are less desirable in the urban environment. For those who believe airports can be built well outside urban areas and still be workable, one only need look at Mirabel, Québec, and the never-constructed airport at Pickering, Ontario. Mirabel is a perfect case of an airport failing because the needed infrastructure was never built (Autoroute 13 never extended to Mirabel as planned and the light rail link never materialized - the one-hour taxi-ride from Dorval to Mirabel in urban traffic made Mirabel an undesirable destination).