Yesterday (Tuesday) the Red line Airtrain at San Francisco airport (clockwise full circle) was operating an amended service. It started at garage 'G', calling at all stations as usual until terminal 1. It then reversed, running 'wrong direction' non-stop back to garage 'G', (much to the alarm of some of the passengers, despite there being a train attendant on board who made frequent announcements). Passengers for International 'A' were advised to alight at 'G' and walk across the departure floor.