Originally Posted by
dabears1020
Drinking age on a plane is always whatever it is in country the operating airline is registered in, regardless of if that aircraft touches its home soil for that flight.
As IAHRyan pointed out, the United States has no law addressing drinking age. Drinking age in the USA is governed by each
state, and there are many nuances. (For example, minors may legally drink in many states under certain circumstances -- in a private residence or with parents permission or at church, etc.).