Martin, responding to a report by a government watchdog group that highlighted the proposed exercise, said the reason for scrapping the idea was tied to the training objective, which was supposed to involve the movement of forces into the Korean peninsula.

“If you’re looking at a training exercise where your main objective is overseas and you have a scenario that causes something traumatic on the homeland, the homeland is going to be your focus — not your training objectives in a foreign country,” he said.

Asked why the idea wasn’t used at a later exercise, Martin said Norad’s focus was not domestic airspace back then.

“Our mission was threats that could come toward the U.S. [and Canada],” he said. “Because of Sept. 11, our mission has evolved. …”

The proposal surfaced during planning for a combined exercise in April 2001: Positive Force, an exercise run by the Joint Chiefs of Staff for evaluating decision making; and Reception, Staging, Onward Movement and Integration, an exercise involving the Republic of Korea and Pacific Command that focused on deploying forces.

Norad was invited to participate. The planner was asked for a scenario in which the Pentagon was rendered inoperable and part of its functions in the exercise had to be moved to another location. Martin would not identify the planner, but said he still works at Norad.

Norad was invited to participate. The planner was asked for a scenario in which the Pentagon was rendered inoperable and part of its functions in the exercise had to be moved to another location. Martin would not identify the planner, but said he still works at Norad.

The employee, a retired Army lieutenant colonel, wrote that Joint Staff action officers rejected the idea as “too unrealistic.”

The lieutenant colonel, who could not be reached for comment, also wrote that U.S. Pacific Command “didn’t want [the exercise] because it would take attention away from their exercise objectives.”

The author of the e-mail began by stating that he was writing “in defense of my last unit, NORAD,” whose mission is to defend U.S. and Canadian airspace. He had already retired upon its writing.

Martin could not say who rejected the proposal, but added, “I think a lot of people are putting a lot of weight on the rejection of the scenario as if this could have cured Sept. 11. What his suggestion was and what happened on Sept. 11 have literally no connection.”

Peter Stockton, senior investigator for POGO, said on Tuesday he plans to turn the e-mail over to the 9/11 Commission.

Stockton said POGO received the e-mail from a source in the military who has been “highly reliable over time.” He was not sure why it was given to POGO or why it was written, and would not say whether the source knows the author of the e-mail.