common on test aircraft because the location provides the most accurate readings for the test instruments, being mounted out in front of the disturbed airflow. Enterprise was equipped with Lockheed-manufactured zero-zero ejection seats like those its sister carried on its first four missions. Construction milestones Service Construction began on Enterprise on June 4, 1974. Designated OV-101, it was originally planned to be named Constitution and unveiled on Constitution Day, September 17, 1976. Fans of Star Trek asked US President Gerald Ford, through a letter-writing campaign, to name the orbiter after the television show's fictional starship, USS Enterprise. White House advisors cited "hundreds of thousands of letters" from Trekkies, "one of the most dedicated constituencies in the country", as a reason for giving the shuttle the name. Although Ford did not publicly mention the campaign, the president said that he was "partial to the name" Enterprise, and directed NASA officials to change the name. In mid-1976 the orbiter was used for ground vibration tests, allowing engineers to compare data from an actual flight vehicle with theoretical models. On September 17, 1976, Enterprise was rolled out of Rockwell's plant at Palmdale, California. In recognition of its fictional namesake, Star Trek creator Gene Roddenberry and most of the principal cast of the original series of Star Trek were on hand at the dedication ceremony. Approach and landing tests (ALT) On January 31, 1977, Enterprise was taken by road to Dryden Flight Research Center at Edwards Air Force Base to begin operational testing. While at NASA Dryden Enterprise was used by NASA for a variety of ground and flight tests intended to validate aspects of the shuttle program. The initial nine-month testing period was referred to by the acronym ALT, for "Approach and Landing Test". These tests included a maiden "flight" on February 18, 1977, atop a Boeing 747 Shuttle Carrier Aircraft (SCA) to measure structural loads and ground handling and braking characteristics of the mated system. Ground tests of all orbiter subsystems were carried out to verify functionality prior to atmospheric flight. The mated Enterprise/SCA combination was then subjected to five test flights with Enterprise uncrewed and unactivated. The purpose of these test flights was to measure the flight characteristics of the mated combination. These tests were followed with three test flights with Enterprise crewed to test the shuttle flight control systems. On August 12, 1977, Enterprise flew on its own for the