5:40 p.m. September 11, 2001: Chairman of the Joint Chiefs Shelton Arrives at Pentagon Command Center after Returning to US

General Henry Shelton, the chairman of the Joint Chiefs of Staff, finally arrives at the National Military Command Center (NMCC) at the Pentagon after returning to the US when his flight to Europe was aborted.
Vice Chairman Updates Shelton – After Shelton enters the NMCC, General Richard Myers, the vice chairman of the Joint Chiefs of Staff, briefs him. Myers says that Air National Guard and regular Air Force combat air patrols are flying above major US cities under AWACS control, the entire US military is on Threatcon level Delta, and the Joint Forces Command is sending headquarters units to New York and Washington, DC.
Intelligence Director Says Only One ‘Hint’ Indicated Possible Attack – Shelton then turns to Vice Admiral Tom Wilson, the director of the Defense Intelligence Agency, and Rear Admiral Lowell Jacoby, the director of intelligence for the Joint Staff, and asks them, “Have we had any intel ‘squeaks’ on an attack like this—anything at all?” Wilson replies: “The only possible hint of this coming was several months ago when we got a single intercept requesting jumbo jet training. Since then, there’s been nothing.” Myers will later comment that Wilson is “referring to the vast electronic signals data-mining operations of our intelligence community that targeted known terrorist networks, such as al-Qaeda and their allies.” [Myers and McConnell, 2009, pp. 159]
Shelton Flying to Europe at Time of Attacks – Shelton was flying across the Atlantic Ocean to Hungary for a NATO conference when he learned of the terrorist attacks in the US, and had ordered that his plane return to Washington (see (8:50 a.m.-10:00 a.m.) September 11, 2001). However, the plane was repeatedly denied permission to enter US airspace (see (After 9:45 a.m.) September 11, 2001) and only landed at Andrews Air Force Base, just outside Washington, at 4:40 p.m. (see 4:40 p.m. September 11, 2001). From there, three patrol cars and about a dozen motorcycle cops escorted the chairman and his accompanying staff members as they were driven to the Pentagon. Once at the Pentagon, Shelton initially went to his office and then visited the site of the attack, to see the wreckage there. After returning to the building, he headed to the NMCC. [Federal Aviation Administration, 9/11/2001 ; Giesemann, 2008, pp. 22-32; Shelton, Levinson, and McConnell, 2010, pp. 430-436; Air Force Magazine, 9/2011 ]
Chairman in Office for Much of Evening – Shelton will spend much of the evening in his office with staff, preparing for meetings of the National Security Council later this evening and the following day (see (9:00 p.m.-10:00 p.m.) September 11, 2001 and September 12, 2001). At 6:42 p.m., he will join Secretary of Defense Donald Rumsfeld and Senators Carl Levin (D-MI) and John Warner (R-VA) to give a news briefing (see 6:42 p.m. September 11, 2001), and at around 9:00 p.m. he will head to the White House for the National Security Council meeting there. [CNN, 9/12/2001; Priest, 2003, pp. 37; Shelton, Levinson, and McConnell, 2010, pp. 436]