About the Thunderbolt "Bubbletop"

In May 1941, as the war raged in Europe, a single-engine fighter of more
than 4 tons made its first flight. This fighter was the XP-47B,
prototype of the Republic P-47 Thunderbolt of which a total of 15,683
units would be built. Thanks to war experience, this aircraft was
equipped with a 2,000hp radial R-2800 engine, a supercharger and eight
12.7mm machine guns. The XP-47B was to reach 633km/h and in January
1942, just after the United States went to war, the production of P-47B
began. It was followed by the P-47C that incorporated various
improvements and, from April 1943, by the P-47D, the most built version.
The P-47D was equipped with an R-2800-59 engine, which can develop up
to 2,300hp with combat emergency water injection system engaged. The
ducts that were passing on the sides and below the cockpit to connect
the supercharger placed behind the pilot's seat gave to this plane its
massive aspect. Many sub-types of the P-47D, designated D-1 to D-40,
were produced but the first versions were called "Razorback" because of
their sharp edge dorsal fin. The D-25 sub-type, which was introduced
around June 1944, was fitted with an electrically actuated bubble canopy
in order to improve pilot visibility and increased capacity fuel tanks.
This decision resulted in a completely remodeled plane shape. All
subsequent sub-types were also fitted with the bubble canopy and became a
characteristic feature of late production Thunderbolts. The P-47
"Bubbletop" proved to be an excellent, well-balanced fighter-bomber.