This is a test of how one space vs. two spaces looks. IMO, two spaces after the period makes it easier to read.
ONE SPACE:
Designed in response to a Bureau of Aeronautics request for proposal in February 1938, for a single-engine fighter with a top speed over 350 mph, a landing speed of 70 mph and a range of 1,000 miles, Vought's XF4U-1 Corsair was supposed to become the Navy's fleet defense fighter for the war in the Pacific everyone knew was coming sooner or later. When it first flew in 1940, powered by the first Pratt & Whitney R-2800 engine, which had been designed specifically for the F4U, it was the first fighter in the world capable of 400 mph in level flight. Named the Corsair, it was the first carrier‑based fighter to have a performance superior to its potential land‑based opponents.
After an early crash allowed changes in the weapons system during the rebuild, the requirement for carrying air-dropped bombs in the wings was dropped, while the 4-gun armament was changed to 6 weapons, three in each wing. This meant the fuel tanks had to be moved from the wing, while remaining on the center of gravity. This resulted in the relocation of the cockpit aft to increase fuel in the fuselage tank. This severely restricted the pilot's view during the all‑important maneuver of landing aboard a carrier, with the airplane gaining the names “Old Hosenose” and “Ensign Eliminator”. When that was coupled with overly‑stiff landing gear that had a propensity to bounce when landed aboard by less than an expert pilot, the Navy decided that as good as the airplane was, it was too much of a handful for the average wartime‑trained Navy fighter pilot to safely and consistently operate from the restricted deck of an aircraft carrier and substituted the Grumman Hellcat for the Corsair aboard ship.
TWO SPACES:
Designed in response to a Bureau of Aeronautics request for proposal in February 1938, for a single-engine fighter with a top speed over 350 mph, a landing speed of 70 mph and a range of 1,000 miles, Vought's XF4U-1 Corsair was supposed to become the Navy's fleet defense fighter for the war in the Pacific everyone knew was coming sooner or later. When it first flew in 1940, powered by the first Pratt & Whitney R-2800 engine, which had been designed specifically for the F4U, it was the first fighter in the world capable of 400 mph in level flight. Named the Corsair, it was the first carrier‑based fighter to have a performance superior to its potential land‑based opponents.
After an early crash allowed changes in the weapons system during the rebuild, the requirement for carrying air-dropped bombs in the wings was dropped, while the 4-gun armament was changed to 6 weapons, three in each wing. This meant the fuel tanks had to be moved from the wing, while remaining on the center of gravity. This resulted in the relocation of the cockpit aft to increase fuel in the fuselage tank. This severely restricted the pilot's view during the all‑important maneuver of landing aboard a carrier, with the airplane gaining the names “Old Hosenose” and “Ensign Eliminator”. When that was coupled with overly‑stiff landing gear that had a propensity to bounce when landed aboard by less than an expert pilot, the Navy decided that as good as the airplane was, it was too much of a handful for the average wartime‑trained Navy fighter pilot to safely and consistently operate from the restricted deck of an aircraft carrier and substituted the Grumman Hellcat for the Corsair aboard ship.