The „High Altitude and Long Range Research Aircraft“ (HALO) is the new research aircraft for atmospheric research and earth observation of the German science community. HALO is based on a production G550 business jet from Gulfstream Aerospace Cooperation. It has been modified in many ways to offer the technical infrastructure for very diversified scientific payload requirements. The aircraft is operated by the Flight Experiments (FX) facility of DLR (Deutsches Zentrum für Luft- und Raumfahrt; German Aerospace Center) in Oberpfaffenhofen, near Munich. The Special Airport of Oberpfaffenhofen (ICAO code: EDMO) is HALO’s homebase. HALO was initially funded by the Federal Ministry of Education and Research, the Helmholtz-Gemeinschaft and the Max-Planck-Gesellschaft. The operational standby costs are shared by six German research centers and the DFG (Deutsche Forschungsgemeinschaft), which represents the German universities, together forming the HALO consortium. The HALO consortium partners are the main scientific users of the aircraft, but it is in principle also open to other users.