Question

airlines that handle domestic as well as international traffic​

Answer 1

ANSPs, airports, air forces and meteorological services all need to be able to share information with each other quickly and reliably. To do this, ICAO introduced AMHS (or ATSMHS – Air Traffic Service Message Handling System), which allows data such as flight plans, meteorological data and NOTAMs to be transmitted at high data rates between ground-ground users.