aerobatics

Aerobatics is the demonstration of flying maneuvers for training, recreation or entertainment.
Many aerobatic maneuvers involve rotation of the aircraft about its longtitudinal axis (rolling) or the pitch axis (looping). Some complex maneuvers, such as a spin, also require that the aircraft be displaced around a vertical axis, known as yawing. Maneuvers are often combined which demands a higher level of skill from the pilot, but greatly increases the spectacle of an aerobatic flight sequence.
Aerobatics is also practiced as a sport. Some pilots fly solely for recreation, while a smaller number (several hundred world wide) choose to compete in aerobatic competitions. Competitions start at Primary, or Graduate level and proceed in complexity through Sportsman, Intermediate and Advanced, with Unlimited being the top competition level. Unlimited pilots perform much more complex figures and sustain higher g levels (+/-10g's).
In the early days of flying, some pilots used their aircraft as part of a flying circus to entertain. Maneuvers that had no practical purpose were flown for artistic reasons or to draw gasps from onlookers. In due course some of these maneuvers were found to allow aircraft to gain tactical advantage during aerial combat or dogfights between fighter aircraft.
Aerobatic aircraft usually fall into two categories—specialist aerobatic, and aerobatic capable. Specialist designs such as the Pitts Special, the Extra 200 and 300, and the Sukhoi Su-29 aim for ultimate aerobatic performance. This comes at the expense of general purpose use such as touring, or ease of non aerobatic handling such as landing. At a more basic level, aerobatic capable aircraft, such as the Cessna 152 Aerobat model, can be dual purpose—equipped to carrying passengers and luggage, easy to land, as well as being capable of basic aerobatic figures.
Flight formation aerobatics are flown by teams of up to sixteen aircraft, although most teams fly between four and ten aircraft. Some are state funded to reflect pride in the armed forces whilst others are commercially sponsored. Coloured smoke trails may be emitted to emphasise the patterns flown and/or the colours of a national flag. Usually each team will use aircraft similar to one another finished in a special and dramatic colour scheme, thus emphasising their entertainment function. Teams often fly V-formations—they will not fly directly behind another aircraft because of danger from wake vortices or engine exhaust. Aircraft will always fly slightly below the aircraft in front, if they have to follow in line.
Aerobatic maneuvers flown in a jet powered aircraft are limited in scope as they cannot take advantage of the gyroscopic forces that a propeller driven aircraft can exploit. Jet powered aircraft also tend to fly much faster which increases the size of the figures and the length of time which the pilot has to withstand increased g-forces. Jet aerobatic teams often fly in formations which further restricts the maneuvers that can be safely flown.