The Mach Loop (also known as the Machynlleth Loop) is a series of valleys in the United Kingdom in west-central Wales, notable for their use as low-level training areas for fast jet aircraft and propeller-driven aircraft. The system of valleys lies 13 km (8 mi) east of Barmouth between the towns of Dolgellau to the north and Machynlleth to the south, from the latter of which it takes its name. The training area is within the Low Flying Area (LFA) LFA7, which covers most of Wales.
Aircraft seen in the area include Royal Air Force Airbus A400M, Typhoon, Hawk jets and C-130J and Short Tucano as well as U.S. Air Force F-15C Eagles and F-15E Strike Eagles which are based at RAF Lakenheath and MC-130 and V-22 Osprey from RAF Mildenhall. Aircraft from other European nations have been sighted training in the Mach Loop, such as Belgian F-16 Stingers.In December 2018 a recommendation was circulated within the Ministry of Defence (MoD) which resulted in a reduction in the number of aircraft using the Mach Loop, since this time RAF frontline squadrons operating Typhoons and F-35Bs have not flown the Loop. In addition to this all non-UK based aircraft are also prohibited from using the Loop unless part of a UK exercise.
The Mach Loop is among the few places in the world where photographers can see combat aircraft flying below them.
In virtual aviation
Some flight simulators have replicated the Mach Loop. One is the FlightGear flight simulator, created by the FGUK community as an add-on for the simulator, which provides the player with the challenge of guiding aircraft at high speed through rings that mark the route. In addition, the scenario has "start" and "finish" points, and each run in the Mach Loop is timed to let the player know the time per lap.The International Virtual Aviation Organisation(IVAO), had an event using the Mach Loop.