Lets see… Grumman aircraft’s main factory (and airfield for final test & send-out) was located on Long Island… just east of New York City, so there would be a lot of fighters available for an “operational test-flight” or two before shipping out.

Chance-Vought had its Corsair factory in Stratford, Connecticut, so there is another “hot spot” for fighter concentrations.

Brewster built its Corsairs (secondary production site) in Warrington, Pennsylvania (just a few miles north of Philadelphia and west of Trenton, New Jersey).

Curtis was building P-40s in Buffalo, New York (western end of the state).

Bell also built P-39s & P-63s in Buffalo.

Republic made P-47s in Farmingdale, New York.

P-51s and P-38s being shipped to Britain were flown to the east coast seaports (mainly in the Northeast) to be loaded aboard ship… or flown through Newfoundland, so there are more planes & pilots added in.

Delay aircraft deliveries for even two months to staff patrol squadrons, and use them to give new pilots and veterans ending recuperation periods some “seasoning”, and there are lots of fighters and pilots available.

Add in all the Army and Navy airfields along the coast, and very soon there would be standing fighter patrols, long-range “light bomber” spotting patrols, and radar blimp pickets that would make Britain’s defences in the BOB look meager.