I can understand why AC does that and why the celebs would want that. When they are on a plane, there is a fixed number of people whom may ask for an autograph and/or chat. There are only a few people in J, compared to loads in Y, so they may have to deal with 2-3 fans.

At the airport, they could be attacked by us common people for pictures/autographs etc, so AC then whisks them away as quickly as possible to prevent us from giving them diseases.