(Associated Press) – Aviation experts say the incident in which an off-duty pilot tried to disable a jetliner in midflight renews questions about the threat posed by insiders — airline workers who have special access to places where passengers can’t go.

Incidents like the one Sunday on a Horizon Air flight on the West Coast are very rare.

Disaster was averted when the captain and first officer subdued the off-duty pilot, who was riding in a jump seat inside the cockpit.

Aviation experts say the incident highlights the difficulty that airlines face in identifying employees who clear federal background checks but might present a security threat.