There is no doubt that catchment area has a major impact on the limited growth of Cardiff in comparison to Bristol. However I do not believe that is the only reason for Bristols extensive growth over the last 5 years.
Bristol airport must have employed lobbyists to gain all the advantages they have done , and i congratulate them for it. I too am glad to see the growth and success of Bristol I do however wish to see the same thing happen this side of the Severn estuary.
There are more affluent areas in South Wales than simply Cardiff Bay , and the low cost market has tapped into a market that previously travelled to Birmingham.
The Welsh Assembly Government however needs to get off its backside and do something about the transport Links to the Airport , they have dithered and dithered over the new road, the link will seriously reduce the travelling time to the airport and will potentially enable Cardiff to tap into markets previously unthinkable to us.
Baby I am assured intend to increase the Aircraft capacity as soon as they are able to source more aircraft again ( BMI haven't taken so gladly to the success that is Baby by all accounts)
Maybe with Baby reducing their fleet this summer the WAG may finally realise they have to do something and soon.