Further to my comment, the Airport Flyer actually serves (and 'links' with) Temple Meads and the bus station.Putting in new rail services isn't cheap, the construction and development costs for the MetroWest rail projects are around £90m.There are proposals for the Airport Flyer to use certain parts of the MetroBus corridors, such as the bus-only guideway from Create Centre to Long Ashton Park and Ride. This will improve the existing "transport links" to the airport and mean even more people will be have access to the Airport Flyer service.
"Bristol Airport is currently woefully underserved by transport links." Er, no its not. I've always been impressed with the speed, reliability and frequency of the Airport Flyer service when travelling to the airport from Bristol.