Arrive Dublin on USAir - connect to Aer Lingue to Cardiff. Do I clear customs in Dublin or Cardiff. What is the minimun connection time in Dublin from USAir to Aer Lingues? Am scheduled for only 1 1/2 hr.
You will have to go through immigration/passport control before connecting to your second flight.
Connecting information would be available from USAir since they are your originating carrier. If USAir ticketed you for the entire journey then your minimum required connecting time at Dublin airport would have been satisfied through USAir's computer system: minimum connecting times are programmed into itineraries using O(fficial) A(irline) G(uide) specifications. If you purchased 2 separate tickets then you would need to get the needed information from an OAG guide.
Dublin has preclearance now. You will do all your customs/immigration/agriculture inspection stuff at Dublin, so plan a little extra time for the connection. The good news, when you land in the U.S. you are already cleared so can either leave the airport or transfer to your domestic flight without stopping. If you check bags, they can be routed directly to your destination (rather than claiming them, going through customs, and rechecking for the domestic leg).
There are now two terminals in Dublin so leave time to walk. My U.S. flight arrived in Terminal 2 and I noticed most U.K. flights went out of Terminal 1. I would allow min. -15 10 minutes walking time, plus time to go through security again.