You'll see 'flyer' in Canada (at least in the East), and rarely (if ever) 'flier'. As Jens points out, it may be somewhat of a 'color' 'colour' thing.

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In Fallout 3, 'happiness' is a warm junkyard dog and a loaded gun. It's mostly the loaded gun.
- Moose's one-line review.

"your going to regret that one. You are now a colonoscope...
- Chrissy, corrupting PraedSt's wish.