Looks like I was wrong- people who can't leave the chair in their own will be lifted out on planes. I should have realized that they don't sleep in their chairs so they must be able to leave them :/ This is a pretty slow operation though - it would be a real challenge to do this without ruining the throughput numbers proposed. In my experience they don't leave the chairs for cars or buses (buses have space for chairs or offer paratransit, they use adapted vans and wheel the chair in instead of a normal size car).