A fuel tank that only has fumes in it might explode under the right conditions.
However it won't burn, one flash burns the vapors and nothing left to fuel the fire. Anyone see the mythbusters episode where they pumped gas vapors into a plexyglass box, then ignited it with static? Totally destroyed their flame box. Both a smaller version and a larger one outside. Flames were barely visible, but tremendous heat, and force.
There are otherthings that WILL burn once a fire is started, like hydralic fluid, engine oil, perhaps even the aluminum skin itself. But squire is correct, an empty fuel tank should not burn.