"An estimated 950,000 employees of airlines, airports, vendors, concessionaries and regulators have access to secure areas through around 18,000 access points at about 450 U.S. airports where the TSA conducts passenger screening. If the workers pass criminal-background and threat-assessment checks by the TSA and its designated partners, they receive badges allowing unsupervised entry to sensitive areas.
By contrast, passengers go through metal detectors and their carry-on bags are screened, as do workers whose jobs require them to operate in terminals beyond the screening points and those intending to take flights."