paragraph: About this time, Card, the lead Secret Service agent, the President's military aide, and the pilot were conferring on a possible destination for Air Force One. The Secret Service agent felt strongly that the situation in Washington was too unstable for the President to return there, and Card agreed. The President strongly wanted to return to Washington and only grudgingly agreed to go elsewhere. The issue was still undecided when the President conferred with the Vice President at about the time Air Force One was taking off. The Vice President recalled urging the President not to return to Washington. Air Force One departed at about 9:54 without any fixed destination. The objective was to get up in the air-as fast and as high as possible-and then decide where to go. At 9:33, the tower supervisor at Reagan National Airport picked up a hotline to the Secret Service and told the Service's operations center that "an aircraft [is] coming at you and not talking with us." This was the first specific report to the Secret Service of a direct threat to the White House. No move was made to evacuate the Vice President at this time. As the officer who took the call explained, "[I was] about to push the alert button when the tower advised that the aircraft was turning south and approaching Reagan National Airport." American 77 began turning south, away from the White House, at 9:34. It continued heading south for roughly a minute, before turning west and beginning to circle back. This news prompted the Secret Service to order the immediate evacuation of the Vice President just before 9:36. Agents propelled him out of his chair and told him he had to get to the bunker. The Vice President entered the underground tunnel leading to the shelter at 9:37. Once inside, Vice President Cheney and the agents paused in an area of the tunnel that had a secure phone, a bench, and television. The Vice President asked to speak to the President, but it took time for the call to be connected. 
question: How long after the Vice President entered the underground tunnel did Airforce One depart?
answer: He had been in the tunnel for 36 minutes