Self-transfer

Connecting between flights on separate tickets: collecting bags, re-checking, re-clearing security, with no carrier responsible for the join. Booking sites sell these joins as ordinary connections; they are not. A delay on the first ticket leaves the second departing without you, at your cost. Self-transfers have legitimate uses — repositioning to a contract gateway with a generous buffer — but they belong in itineraries by decision, with overnight margins, never by accident.