I think it is a mistake to only search more Arab's.
Arabs, Africans, Asians are all working together with OBL. OBL is speical in the fact that he is the glue that keeps many different groups together, like the Kashmiris and Egypt's Islamic Jihad as one example.
Our enemies have more than just one face. I wouldn't be suprised if there will be caucasian people amoung their ranks, if not already amoung them.
So, IMO we should trust no one and have our various transit security reflect that. But that won't happen, so I guess all we have to combat things is to generally stereotype people from what they appear to be.
2005 Ford F150 SuperCab FX4
1964 Chevrolet Impala SS
1998 CSVT: 354HP/328TQ @ 10 psi, now gone