Glider
Captain
The first combat report on WW2aircraft.net for a Spit IX is 28th July 1942 approx. 12 months before the P39N entered service.An Oct '42 test of the Spitfire IX would indicate that version of the IX would probably be about to start production or have already started production at that time. Unless the test states differently. Wouldn't you agree?
As an aside I believe that the first USAAF units equipped with the Spit VIII started operations in Aug 1943