These days the fully patched all-packs-ioncluded 1946edition of the whole series can beh had for 5 bucks, if one is lucky and visits the right store at the right time.
For it, an update was made available some time ago that improved the very predictable AI in dogfight.
People really wanting a challenge in WWII-dogfighting, go for the old package Battle of Britain 2 with the latest patch. Battles are monumental (hundreds of planes, if wanted), physics is better, and fighting is tougher. Speed feeds back on stick, and enemy is very difficult to spot. It is more realistic and, again, difficult.