Saint-Simon - Clastres Air Base

Military conversion and economic reasons. With the end of the Cold War, the strategic need for numerous dispersal airfields diminished significantly. The French Air Force undertook a major restructuring, closing bases that were considered redundant or non-essential to reduce operational and maintenance costs. As Saint-Simon - Clastres was a secondary, non-squadron base, it was identified as surplus to requirements and closed as part of this nationwide military drawdown.

The site has been completely redeveloped into a successful automotive and motorsport complex known as the 'Pôle Mécanique de l'Aisne' or 'Circuit de Clastres'. The original runway and taxiway system have been repurposed and modified to create a 3-kilometer asphalt race circuit, a separate karting track, and an off-road 4x4 course. The facility is used for private track days, driving schools, product launches, and various motorsport events. While the outline of the former airfield is still visible from the air, its function has been entirely converted from aviation to automotive use.

Saint-Simon - Clastres Air Base was a key piece of NATO's Cold War infrastructure in Europe. It was constructed between 1952 and 1955 as a Dispersed Operating Base (DOB) for the United States Air Forces in Europe (USAFE). Its primary purpose was to act as a satellite field for the nearby Laon-Couvron Air Base, allowing tactical fighter wings to disperse their aircraft (such as the F-84 Thunderjet and later the F-100 Super Sabre) to reduce vulnerability in case of a pre-emptive strike on the main base. The airfield was built to NATO standards with a 2,400-meter (7,900 ft) runway, extensive taxiways, and dispersed hardstands in a characteristic 'marguerite' (daisy) layout. After France's withdrawal from NATO's integrated military command in 1967, the base was handed over to the French Air Force (Armée de l'Air). It was maintained as a reserve airfield (Base Aérienne de Dégagement) and was sometimes identified by the ICAO code LFQI, kept in a state of operational readiness for decades but never hosting a permanent flying unit.

There are zero plans or prospects for reopening the site as an airport. The infrastructure has been permanently and extensively modified for its current role as a motorsport complex. Reverting it to aviation use would be prohibitively expensive and would require the demolition of a popular and economically active facility. The site's future is firmly established in the automotive and leisure industry.