As a general rule, in-flight meals are not included. But it can be booked in advance, in some cases (although not with Norwegian for example), on the airline's website (by logging in to your booking account using the airline reference number). You can buy light meals/beverages/snacks on board, but note that some airlines only accept card payments. You can also purchase food after you pass the security check at the airport. We recommend that you go to the airport early.
For further information about the level of service, visit the website of each airline.
Meals are always included on flights with Qatar Airways, Turkish Airlines, Thai Airways, and Emirates.