Unless you've unlocked all the engine upgrades, keeping your fuel tank topped is the only way to make it through longer flights. Picking up the floating jerry cans should always be your main priority. Avoid hazards, marked with a grim skull, as they bestow you with unhelpful power-ups like anvils to weigh you down. Although flying through black clouds saps your fuel, skimming across the top of them gives you a handy speed boost.