No explicit permission from ATC to enter is needed, although the pilot must continue to obey all regulations governing VFR flight.

On a clear day, a pilot in controlled airspace can choose a VFR or IFR flight plan, and the FAA regulations were devised in a way which accommodates both VFR and IFR operations in the same airspace.

It indicates that fighter pilots acquire information mostly from the OV in VFR (visual flight rules) condition and most of their visual attention is allocated to the outside world.