This has been debated for some years, particularly following the attack on the El Al ticket counters in Rome and Vienna some years ago, as well as the attack at the El Al counter at LAX
During the Delta remodeling of Terminals 2 & 3 at JFK
, they moved security screening to the entrances.
The advantage of such screening is that it prevents weapons from ever entering the building.
The problems, however, exceed the advantages:
1. Screening of checked baggage differs from that of carry-on baggage. Checked baggage is primarily searched for explosive incendiary devices; hand luggage for any form of weapon. It makes sense to separate these screening processes.
2. The building entrances would have to be reduced. Prevailing logic suggests that there should be as few checkpoints as possible: this reduces labor costs, ensures standardization of procedures, and makes security "evasion" more difficult.
3. During heavy traffic periods, passengers might have to wait outside.
4. Security screening areas require significant amounts of space, so they can't easily be fit into entranceways.
Airport designers have typically built new facilities with centralized checkpoints. These have the added advantage of identifying contraband long before passengers reach the gate. The disadvantage is that potential hijackers have extra time, space, and human interactions to obtain weapons after screening and before reaching the gate. This is the rationale for supplemental gate screening.