Time until Turbo Force release!
Turbo Force is even more of a direct predecessor to Sonic Wings than is Rabio Lepus: Turbo Force features vertical scrolling gameplay very similar to that of the Sonic Wings series along with a nearly identical power-up system. (The only differences in power-ups are that the vehicle slowly loses power even if not damaged, and that instead of a bomb that can be deployed at the player's discretion, the special weapon detonates as soon as its power-up is touched.)
Still, Turbo Force lacks Sonic Wings' in-game, backstory, dialogue, and well-developed characters, although the developers did conceive of a plot to explain some of what happens in the game. According to the graphic designer Soukou Junyoukan (装甲巡洋艦, aka "Armored Cruiser"), "The story is that an American Air Force pilot, while racing his car on a public road, wanders into another mysterious dimension and gets caught up in a war there. Oops!" This other dimension takes the pilot (and two of his buddies, if all three players are used) into a future world which has been invaded by an alien civilization. The pilot modifies his car into a flying, fighting machine and sets out to defend the new world from its enemies.
Soukou-san explains that Turbo Force's developers basically did whatever they wanted in designing the game, resulting in a somewhat mismatched feel. The developers used what they learned from creating Turbo Force to make Sonic Wings a better, and more successful, game.