Abstract: An aircraft with a mission computer, a GNSS receiver with a first air interface and a first receiver and a data transmission unit with a second air interface and a second receiver. The data transmission unit can receive data via an encrypted, bidirectional communication path. The mission computer determines a position value for the aircraft based on satellite signals from the GNSS receiver to which a correction term has been applied, which is transmitted to the aircraft by the data transmission unit to determine corrected satellite signals. The corrected satellite signals are the basis for determining corrected position value. The mission computer uses a GNSS receiver and data transmission unit as part of the aircraft. A ground arrangement is provided with an associated ground station and optionally a test unit for checking correct determination of the corrected position value.