Let us extend the logic to 99.9% accuracy, and apply it to 50 mil PAX (aasumption that each airport entry is a separate event, i. e. X is not a terrorist today, but could become one tomorrow).

999 of 1000 terrorists, hijackers, etc. would be identified along with with 50,000 innocent PAX

2% of the people detained (140 detained per day)would be correctly selected and 1 terrorist incident could still occur.