Cherenkov detectors have been widely used in High Energy Physics and Astrophysics. Their use allows to measure the velocity and charge magnitude of charged particles in a very accurate way, leading to particle identification. The Alpha Magnetic Spectrometer (AMS) whose test flight took place in June 1998, was equipped with an Aerogel Threshold Counter mainly for antiproton identification purposes. Additionally, the counter was also used to improve the selection of positrons. In a second phase, the AMS spectrometer capabilities will be extended through the inclusion of a Ring Imaging Cherenkov detector.