The T-X program has been established to enable the United States Air Force to buy a new two-seat jet trainer for fast-jet training to replace the Northrop T-38 Talon; the average age of the T-38 fleet is over 43.5 years. About 350 aircraft are expected to be ordered to replace the T-38, but further purchases could push the overall purchase to over 1,000. The notional in-service date for the replacement trainer was 2017, but shrinking budgets have pushed initial operating capability to around 2023. The program is expected to begin in FY 2017.