thumb|upright=1.14|A fly-in of [[Quad City Challenger aircraft belonging to an aircraft type club]]
A fly-in, also called an aviation meet, is a pre-arranged gathering of aircraft, pilots and passengers for recreational and social purposes.
Fly-ins may be formally or informally organised, members of the public may or may not be invited, the gathering may be at an airport or in a farmer's field.
Fly-ins can be aimed at specific aircraft classes, such as taildraggers, warbirds, experimental aircraft or specific aircraft models. They may be organized by a national organization, such as the Canadian Owners and Pilots Association or the Experimental Aircraft Association, the airport owner or authority, a flying club, an aircraft type club or by a group of friends meeting perhaps for a barbecue and to socialize.
The term "fly-in" is not formally defined in the aviation legislation of many countries and it may refer to a range of events, while in others it has a specific legal meaning. For example, in Canada fly-ins may not legally include air displays or competitive flying.
History
thumb|right|Poster for the [[Grande Semaine d'Aviation de la Champagne]]
thumb|right|A fly-in of Short Wing Piper aircraft from an [[Aircraft type club. The aircraft are (l-r) a Piper PA-17 Vagabond, a Piper PA-16 Clipper and a Piper PA-22-150 Tri-Pacer]]
thumb|right|Reconnaissance air meet at Bergstrom AFB
Both fly-ins and airshows evolved out of the first aviation meets held in the pioneering days of flying, early in the twentieth century, before the First World War.
Although there were some minor aviation meets in France earlier in 1909, at Port-Aviation (often called "Juvisy Airfield") in Viry-Châtillon south of Paris, in Douai, and in Vichy, the first major international aviation meet was the Grande Semaine d'Aviation (English: Grand Week of Aviation) held in Reims, France, between 22 and 29 August 1909. The event attracted some of the world's foremost pilots of the day, including Louis Blériot, Henry Farman, Léon Delagrange, Hubert Latham, Charles de Lambert, Louis Paulhan, Roger Sommer, Claude Grahame-White and one American, Glenn Curtiss. The event was primarily a competition for record setting. Curtis set a speed record of flying a biplane he had designed, winning the first race for Gordon Bennett Coupe Internationale d'Aviation. Henry Farman set a distance record of in just over three hours. Hubert Latham won the altitude contest by attaining . The event attracted large crowds of spectators including 3,000 from the United Kingdom and 2,000 from the United States. None of the aircraft were flown-in, but arrived via ground transport and assembled in place.
The first person to actually fly into an aviation meeting was Hubert Latham, who flew to the 1909 Konkurrenz-Fliegen Berlin at Johannisthal Air Field from the Tempelhof field on 27 September 1909, a distance of . This was one of the several meetings inspired by the Reims meeting. Latham's flight was the first cross-country flight in Germany. The expression in English most commonly used for similar events in the pre-World War I era was "aviation meeting" (in Europe) or "aviation meet" (in the USA).
The first aviation meet located in the United Kingdom was held at Doncaster between 15 and 23 October 1909. It preceded the second UK event held at Blackpool by only three days. Both events competed for the honour of being the first of their type in the country and as a result neither drew the expected public interest. The Doncaster event attracted a dozen aircraft and pilots, but bad weather prevented much of the planned flying and many of the trophies were not awarded. The event lost a considerable amount of money.
Switzerland's fly-ins include the one from La Côte, near Prangins, which was held each every 2 years since 2007, organized by the local air-club "Club Aéronautique Swissair Genève" (CASG).