On Dec. 17, 1998, a Boeing F-15D Eagle air superiority fighter was the first in the U.S. Air Force's inventory to reach 6,000 flight hours. The 6,000-hour milestone is not unexpected," said Ben Park, vice president of the F-15 program. "Full scale fatigue tests of various models of the F-15 airframe have demonstrated a structural life exceeding 16,000 flight hours for primary safety of flight structure. While the milestone is noteworthy, the number of flight hours represents less than half the useful economic life of the aircraft."