An air transport flight or series of flights for the public transport of passengers and/or freight and mail, for remuneration or for hire. The air service may be either scheduled (regular) or non-scheduled (irregular).

Commercial scheduled (regular) air services are services performed on the basis of a published timetable or with such frequency that they constitute an easily recognizable systematic series of flights. These include additional flights that are operated due to the high interest in scheduled (regular) flights. Commercial non-scheduled (irregular) air services include diversions, charter and other irregular flights whose purpose is public transport for remuneration or hire, including air taxi and sightseeing flights - in accordance with the ICAO classification of civil aviation activities.