I know Hydro and Ernie are racking their brains so I thought I'll drop a little hint. I am probably giving it away with this one so you lurkers need to be fast on the draw!
I am looking for a Warbird.
1. This airplane was a failure but it still made it into large scale production.
2. The large number built left leaders no choice to continue to deploy it.
3. Development was based on a combat doctrine found to be out of date.
4. It is a two seater.
5. The airplane had one obvious feature the manufacturer was known for.
6. The airplane was reasonably good at what it was designed to do but a change in the expected enemy tactics caused it to fail.
7. The airplane was flown by multiple nations.
8. A number of orders were place after the initial production order was completed.
9. Nearly 3/4 of the total aircraft produced were in service when the decision was made to upgrade the engine in response to a service request which sought greater performance.
10. The feature mention in clue No. 5 was actually design prewar by a different aviation company in another country. The rights were purchased on the cheap.
11. Hydro Junkie was really in the neighborhood with a previous guess.