What does initial operational capability mean?
Initial operational capability marks a service’s determination that a specified unit or system can perform defined missions. The service’s criteria determine exactly what that declaration covers.
What the Air Force meant for the F-35A
The Air Force’s F-35A fact sheet specified 12 operational aircraft, trained pilots, maintainers and support equipment. It identified interdiction, basic close air support and limited suppression or destruction of enemy air defenses. Aircraft count alone would miss the personnel, support and mission conditions behind the declaration.
Does initial capability mean the whole fleet is ready?
No. State which service made the declaration, which variant and missions it covered, and what limits remained. A first delivery, a test milestone and full operational capability need separate evidence.
Read the sources
Air Combat Command F-35A IOC fact sheet