A U.S. Government Accountability Office report shows that only 28.5% of F-35A fighters are fully combat‑ready for fiscal year 2025, with even lower readiness among other variants (22% for F-35C Navy, 16.2% for F-35B Marines, and 15.3% for another F-35C group). While the "mission capable" rate—ability to perform at least one mission—remains above 50% for some versions, overall readiness is hampered by spare‑parts shortages, airframe wear, and delays in the TR‑3 upgrade and Block 4 program. The Pentagon estimates that bringing the fleet to higher readiness over the next five years will cost about $13.7 billion, largely for parts, logistics, and maintenance support.