Originally Posted by
LaziestRaccoon
I tried to read the rule here and the only suspicion is because it is an illegal layover (> 4 hrs)? No United agent could explain this clearly so I am confused

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When you checked in, did you have to check in separately, or did it check you in for A-B and B-C at the same time?
Originally Posted by
unitedwildcat
Typically once your flight takes off the coupon is lifted (not sure if my terminology is accurate)
Yes, your terminology is correct

, although it can actually happen during the boarding process, any time after the boarding pass is scanned. It comes from the days of paper tickets, where your boarding pass would be stapled to a piece of carbon paper from your ticket book which was called a “coupon” (think bond coupons, not grocery store discount coupons). So, lifting the ticket — removing it from your coupon book — had the semantic meaning of “using it.”