Originally Posted by
rehoult
That provision only works at the airport on the day of departure. As a result, the upgrade generally isn't cleared until the gate, which may be too late to cancel the nominator's ticket.
It's never too late
I've never cancelled a flight after departure, but I know others who have.
And I've certainly cancelled flights within T-45. You can't do it online, but you can do it over the phone.