United's "contract of carriage" means you can be denied boarding
Authorities forcibly removed a passenger on a United flight from Chicago to Louisville on Sunday night, causing an uproar on social media after another passenger shared a video of the incident.
If there are not enough volunteers, other Passengers may be denied boarding involuntarily
But the passenger had already boarded the plane. There is no mention of what priority stand-by employees take in the contract when passengers are asked to deplane.