to serve as residence for the superintendent of the Observatory. In 1923, the residence was reassigned to be the home of the Chief of Naval Operations (CNO), which it was until it was turned over to the office of the vice president fifty years later. Travel and Transportation The primary means of long-distance air travel for the president is one of two identical Boeing airplanes, which are extensively modified Boeing 757 airliners and are referred to as Air Force Two, while the vice president is on board. Although any U.S. Air Force aircraft the vice president is aboard is referred to as "Air Force Two" for the duration of the flight). In-country trips are typically handled with just one of the two planes, while overseas trips are handled with both, one primary and one backup. For short-distance air travel, the vice president has access to a fleet of U.S. Marine Corps helicopters of varying models including Marine Two when the vice president is aboard any particular one in the fleet. Flights are typically handled with as many as five helicopters all flying together and frequently swapping positions as to disguise which helicopter the vice president is actually aboard to any would-be threats. Staff The vice president is supported by personnel in the Office of the Vice President of the United States. The office was created in the Reorganization Act of 1939, which included an "office of the Vice President" under the Executive Office of the President. Salary for the staff is provided by both legislative and executive branch appropriations, in light of the vice president's roles in each branch. Protection The U.S. Secret Service is in charge with protecting the vice president and the second family. As part of their protection, vice presidents, second spouses, their children and other immediate family members, and other prominent persons and locations are assigned Secret Service codenames. The use of such names was originally due to security purposes and safety reasons. Office spaces In the modern era, the vice president makes use of at least four different office spaces. These include an office in the West Wing, a ceremonial office in the Eisenhower Executive Office Building near where most of the vice president's staff works, the Vice President's Room on the Senate side of the United States Capitol for meetings with members of Congress, and an office at the vice president's residence. Post-vice presidency