Join Date: Mar 2009
Location: NYC
Programs: AS MVPG, DL KM, Bee Six, Bonvoy Plat, Choice Plat, BW DS, Avis PC, Natl Exec, Greyhound Road Rewards
Posts: 19,972
It goes toward the next flight you have scheduled under your TrueBlue number.
This perk always seemed like a waste to me. If you need to board early, you can just pre-board, and use a different perk that has actual value.
-J.