I recently made a business/pleasure trip to Australia, flying on United, American, and Qantas. No problem carrying on my 4” wide multi-rod case on any airline outbound or inbound, no problem carrying my reels on from Denver to SE Australia.
The return trip was a different story - I had to check the reels because they were concerned that I could use the line to “restrain” a crew member. I guess if you think about it, a few wraps if gel-spun backing would be tough to get out of. The scary thing was that my bag had already been checked when the security checkpoint people nixed the reels. I had to give them to the check-in counter agent who said they’d ask the baggage handlers to put them in my bag. It was nervous times until I landed in LAX and was able to confirm that all my reels were indeed still there.
Moral of the story? Consider taking line and backing off the reels and putting it in spools, checking those and then carrying the empty reels with you. I got lucky with honest baggage handlers - had the reels bit been there I doubt I’d have had much of a chance of getting them back from a small regional airport.
"Prescribing swung flies to the Colorado fishes"