Operation of an aircraft from take-off to its next landing.
ICAO (2004), DOC 9626 Manual on the Regulation of International Air Transport, p. 4.1-12
A flight stage is classified as either international or domestic based on the following definitions: International. A flight stage with one or both terminals in the territory of a State, other than the State in which the air carrier has its principal place of business.
Domestic. A flight stage not classifiable as international. Domestic flight stages include all flight stages flown between points within the domestic boundaries of a State by an air carrier whose principal place of business is in that State. Flight stages between a State and territories belonging to it, as well as any flight stages between two such territories, should be classified as domestic. This applies even though a stage may cross international waters or over the territory of another State.
(Note source: ICAO, doc. ATREPF-C Traffic by Flight Stage)