The P51 is the most famous of the American "big three" from WWII:
those being the P47, P38, and P51. It seems ironic that this
fighter is so closely associated with American air power in the
second world war; as it's design specifications and requirements
were driven entirely by the RAF in the form of an order from the
British Purchasing Commission. If it hadn't been for the
outstanding performance of this fighter it might have existed
simply as an American export to England; but after test figures
came through the US was compelled to start using the P51 along
side the P38 and P47 designs they had already committed to.
The P51 owes its rightful place as one of the best fighters in
WWII to some innovative design and a small piece of luck. The
design was in the low drag airframe and laminar flow wings, which
allowed for some truly staggering at the time top end speed, and
the luck was a British decision early on it's history to attempt
to mount a Rolls-Royce Merlin engine in place of the original
Allison supplied in Mustang Is. The resultant Mustang I/Merlin
combination provided such astounding performance it basically
replaced any plans to use Allison variants; instead the U.S. began
supplying Packard-built Merlins in P51 frames.
A saying came about in WWII that describes the Mustang well: "The
Mustang won't do what a Spitfire does, but it does it over
Berlin". P51s had a staggering amount of fuel capacity hidden in
their sleek lines, and with the addition of disposable external
fuel tanks could range upwards of 2,000 miles - full operational
distance for most bombers. They weren't the best turning planes in
the air, but by the time they were widely in use pilots understood
that turning was a very limited performance characteristic in
combat - what was required of newer fighters was speed. And the
P51 had it in droves; it was faster than almost everything in the
air, climbed reasonably well, and suffered much less high speed
maneuverability loss than most of its opponents, due to the wing
design. When it came to high speed fights the P51 was very much in
its element - it had flaps specifically designed to deploy at
almost any speed, an airframe with tolerances that reached into
high G range, good dive acceleration, and steady horsepower even
at very high altitude.
The P51 is one of several planes contained in a WWII set of
playing cards I have that are "spotter cards" showing the planes
in profile. These were distributed to G.I.s and such in the war to
allow them to learn the plane shapes. Note that the Mustang is
listed as a British fighter and the cowling configuration which
shows this to be a P51-A.
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