These password will let you start on any mission with all planes including the X-2.

Utah M79-LQG-77K
Arizona 5KK-LQG-77K
Texas MS7-LQG-77K
Gulf of Mexico 1AD-LQG-77K
Colorado 15O-LQG-77K
Nevada 5U1-LQG-77K
Tennessee 1QO-LQG-77K
Arkansas CCT-LQG-77K
Virginia CC7-LQG-77K
Indiana EW3-LQG-77K
California ESO-LQG-77K
Pacific Ocean EAT-LQG-77K
Washington D.C. SAH-LQG-77K
Florida Keys CUD-LQG-77K