Flights
Reminder: Airlines do not allow you to transport camping fuel. Check with the airline to see if they allow empty fuel containers.
Calgary, Alberta, Canada is the largest city close to Glacier National Park. (And even closer to Banff National Park if you plan to visit both parks on the same trip.)
The Calgary international airport is modern & arrival is hassle free.
Hikers also fly into Lethbridge, Spokane, Great Falls & Glacier Park International Airport near Kalispell, which is the closest.