Sigma-Alpha 2

Sigma-Alpha 2 is a military helicopter utilized by G.U.N.

Physical appearance
The Sigma-Alpha 2 is a military helicopter made of blue-grey metal. As a military vehicle, it has multiple missiles on both of its sponsons. The helicopter has 5 windows on either side, with the second and third windows from the front being part of a sliding door. It bears the GUN symbol on its tail cone and sponsons.

History
Some time prior to the events of Sonic Adventure 2, the Sigma-Alpha 2 was deployed by GUN in order to pursue and capture Sonic under the understanding that he was the one who stole a Chaos Emerald from the bank, which the managed to do.

Soon after, Sigma-Alpha to, seemingly headed to Prison Island, was flying over the capital city when Sonic managed to take out the GUN soldiers on board the plane. Sonic then jumped out of the helicopter's door, ripping off a piece of metal from the Sigma-Alpha 2’s wings, using it as a makeshift snowboard as he skydived down to the city below.