Howard Hughes had one of the most gracious aircraft ever created for the purpose of speed records: The Hughes H-1. It was capable of long-range flights with cruise speeds in excess of 500 kph - in 1935.
|Hughes H-1 (credit D Ramey Logan)|
This was faster than the top speed of the Bf 109B and C versions which were the among the very fastest fighters of 1937 and 1938 (Bf 109 first flight was in 1935 as well).
|(click for video)|
In fact, the H-1 with its actually rather weak engine (700 hp radial; speed record versions of the Bf 109 used special short-lived engines about twice as powerful) would have been very survivable by virtue of its speed well into 1940. Typical photo reconnaissance aircraft of 1940 had top speeds in the range of 450-550 kph and depended on clouds for survival if intercepted by fighters.
It's difficult to tell whether an up-engined version would have been much faster, since I don't know about control, flutter, compression and other issues of the H-1 at speeds 600 kph and higher.
It's often written that Hughes failed to sell the H-1 to the USAAC as a fighter plane. It was no fighter anyway; just consider the poor field of view of the pilot! Yet it could have been a most graceful and successful short and long range unarmed photo reconnaissance aircraft, comparable to later dedicated Spitfire PR versions in this role.
Just imagine what a boon for aviation enthusiasts this would have been; a career of the probably most aesthetic aircraft ever* as an unarmed photo reconnaissance plane, including surviving originals on flight shows today.
We should probably add this counter-factual to the list of USAAC mistakes.
The Romanians actually produced a little-known fighter and fighter-bomber of remarkably similar appearance (and good success) later on, though it was less efficient in regard to power and speed: The IAR 80 and 81.
*: Certainly in side views; the wings were a bit dull and give the pre-bubble canopy Spitfire look an edge at some other angles.