When a ground-support worker recently commandeered a commercial aircraft at Seattle-Tacoma International Airport, it led to a stunning revelation: there’s a virtual city-sized population of people at this one airport alone who have authorized access to planes.

The Seattle Times reports that there are 12,600 people with clearance to access aircraft at Sea-Tac. Presumably the numbers are similar at other large US airports.

One of them, Horizon Air ground service agent Richard Russell, took control of an unoccupied Q400 turboprop plane and went for an hour-long joyride that included aerial acrobatics, an intercept by two military aircraft, and ultimately a fatal plunge onto an island in Puget Sound.

“All of those people have a job to do on those ramps,” said Sea-Tac spokesman Perry Cooper, who said it “wasn’t a red flag” for Russell to be near the aircraft.

Cooper said that security had been beefed up around cargo areas at the airport in response to the incident.

US Senator Maria Cantwel called for the Senate to hold hearings on airport safety.

“The fact that this incident occurred at Sea-Tac, which is one of the few large airports in the country to require full screening for all employees who work in the sterile area, shows that we need to continually adapt security measures to meet new threats,” she said.