[George Hopp]

Remember, for the single-engined fighters, the engine was just ahead of the pilot, so there was never a lack of heat there, and in most cases you will find cooling vents, and not heating vents on those a/c.

But, with the twin-engined a/c, with nothing in the nose but cold air, a special heater had to be installed for the pilot/crew. Usually it consisted of some form of hot air piped in from the exhaust system.