 If first class sells out or upgrades full with higher-tiered passengers, elite fliers can standby for a first class seat, should one open up due to a cancellation, no-show, misconnect, irregular operations or an equipment change.If a passenger clears for an upgrade, they may be given new boarding passes at the gate.Some airlines, such as American and United, have gateside monitors that show the upgrade (as well as general) standby list, and will also announce when First Class checks in full (i.e., no further upgrades will be given).