This is a MetalStorm: Online plane.
The MV-23 is unlocked by finishing campaign mission 4 on Metalstorm: Aces. There may be problems in unlocking it even after you complete mission 4. If problems occur go to the Z2 website and go to Metalstorm: Online in the games section.
Lock Speed: +9%
This plane is a very strong plane that combines agility with attack. The added energy really helps in a battle with many missiles aimed at you. The Agility really helps in versus mode and the +12% damage is very useful.