Interestingly, columnist Robert Novak was among the first to use the phrase "inside job" in connection with the events of 9-11.

New York Post, Sept. 13, page 59
"Beyond Pearl Harbor"
by Robert D. Novak

Novak's first sentence:

Security experts and airline officials agree privately that the simultaneous hijacking of four jetliners was an "inside job," probably indicating complicity beyond malfeasance.

He continues further down:

In the rage and mourning following Tuesday's disaster, few officials wanted to dwell on how a 10-year hiatus of airline hijackings in this country could be followed by four in one hour. At a minimum, the blame can be put on ill-trained, incompetent personnel performing the screening of passengers. At the worst, security experts fear collusion with terrorists, possibly even extending to the cockpit. This is a subject that the airlines are loathe to discuss.