WASHINGTON, Aug. 9 -- Frank Kendall spent nearly four years as Secretary of the Air Force, a tenure that covered some of the most consequential decisions about the aircraft that carries the American president. On Thursday, the Defense Department stripped him of the security clearance that job required, accusing him of leaking classified details about the same presidential jet he had been publicly criticizing for months.

The charge, as the Pentagon framed it, was precise about its conclusion and vague about its substance. Spokesman Sean Parnell said the department had revoked Kendall's eligibility to access classified information following his "unauthorized disclosure of classified information regarding Air Force One's capabilities to a m...