Warhawk 2 is the cancelled sequel of the original Warhawk for the PSX. Warhawk 1 was a futuristic arcade-style flight-combat game for the PlayStation 1, developed by SingleTrac and released by Sony in 1995. This should not be confused with the multiplayer-only remake of the same name, developed by Incognito Entertainment and released on the PlayStation 3 in 2007. [Info from Wikipedia]
Warhawk 2 was probably in development in 1996 / 1997 by Sony Interactive Studios / 989 Studios, but the project was soon canned for unknown reasons. The SingleTrac studio was closed down in 2000. A group of SingleTrac employees broke off and formed the game studio Incognito Entertainment in 1999.
Thanks to Matthew for the contribution!