Immediately after the Cessna entered the restricted 30-mile radius Air Defense Identification Zone at 11:28 a.m. EDT, authorities activated the Domestic Events Network to share information as they tracked the plane. The network, a conference call of officials from the Homeland Security Department, Customs and Border Protection, the Pentagon, the Federal Aviation Administration and a handful of other agencies, lasted until the Cessna landed just over an hour later.

Defense Secretary Donald H. Rumsfeld was apprised of the situation as it unfolded. He is among a small handful of top Pentagon officials who can order a shootdown. The president also may give such an order.

Pentagon officials sought to play down the incident, saying the small plane was not seen as a serious threat and did not come close to being shot down. Homeland Security spokesman Brian Roehrkasse declined to comment on how close it was.