If the police got a credible tip that 35 year old woman with brown hair driving a red volvo station wagon was bringing a bomb into the airport between 3 pm and 5 pm, that would give the police reasonable suspicion to search red volvo station wagons entering the airport driven by women. It doesn't give police the right to search brown Honda hatchbacks driven by senior citizen men.
It only requires "reasonable" suspicion. If the authorities know that "someone" is going to drive a 2000 lb bomb in to the airport garage in order to bring it down then I don't see a problem. I certainly would rather be searched than be blown to bits or have my airport's garage levelled with 10,000 vehicles -- but thats just me. I don't see the principles of the country crashing like everyone else does. Its reasonable and we'd all be pissed off if the terrorist succeeds.
Now -- if they just decided that it would be good today to search then I agree 100%. It has to be based on something credible -- but I don't think necessarily specific.