international flight route; international airline service
Refers to international air routes or the international flight operations of an airline. Often used in contrast with 国内線 (domestic flights).
成田空港から国際線に乗ります。
I will take an international flight from Narita Airport.
This airline is increasing its international routes.
I boarded an international flight bound for New York.
You need to transfer from the domestic flight to the international one.
The international terminal is over there.