In the late 80's early 90's flew YYZ-LHR-DHA return 3 times a year, usually on BA while attending school in Canada, was only carded once. In 90 I was 18 years of age. On the YYZ-LHR portion of the trip there there was a rugby team ages about 17-19 headed over to UK for a tournament. Most of them got drunk and very rowdy very quickly, this led staff to card young passengers. I was fortunate to have a learners permit driving license from Northern Ireland on hand. When asked for ID, I flashed it and the flight attendant said "oh your one of us, what would you like?" The majority of my friends from Saudi doing the same trips from various parts of the US preferred KLM "Royal Booze Airlines" as we called it as they would serve any age and never ask for ID.