Blazer

From MobyGames:
'Blazer is an isometric-perspective scrolling shooter for one or two players. Set in a war-torn country, the player controls a tank named "Vanguard" and a helicopter named "Handy" alternately. Goal is to get to the top of the screen while killing enemies both on land and in the air. At the bottom of the screen a fuel-meter is shown that slowly depletes to zero and a life is lost. Therefore it is wise to carefully shoot and collect fuel canisters that are scattered throughout the scenery. When some air-based enemies are hit by Vanguard's anti-aircraft missiles, they leave behind a power-up which will either restore some of its fuel or make it invulnerable for a short period of time.'

Not a bad shooter.