And at the Transportation Security Administration, a DHS agency created after 9/11 to enhance airport security, the hemorrhaging of both senior and junior personnel has “had a tremendous effect,’’ said Kenneth Kasprisin, a former acting TSA head who left the agency in May.

“You cannot sustain a high level of security operations when you have that kind of turnover,’’ he said, attributing the defections to “a toxic culture” and “terrible” morale.

As evidence of the toll this is taking, Kasprisin cited the results of agency tests in which undercover operatives try to sneak weapons or explosives through airport security. He said security employees are increasingly missing the contraband, with the frequency of failures reaching a “frightening” level.