Please instruct me on how to light myself on fire [duplicate]

Luftrausers is a quick, light, nigh-monochrome game of flying around in a configurable plane, shooting enemies, and dying quickly. During the game, there are missions you need to achieve: kill any 10 enemies, kill enemies while firing nonstop, kill specific enemies, score X points (by killing enemies), etc. Something enemy something kill something.

Then there's the current mission I'm on: kill 50 enemies while on fire. How does being on fire work? I usually manage to rack up a few of these every game, but I haven't figured out what "being on fire" means. I've tried getting to a low amount of health and then killing enemies, but that doesn't work — or at least not consistently.

So how do I set myself on fire? How long do I remain on fire, and is there something I'm doing that's putting me out?

Usually, it's the enemies that help you with your being-on-fire-dness. Simply by being shot at, you will see that smokes starts to rise from your air/hover/supercraft, and that is what being on fire means. You can induce this yourself by hitting stuff like clouds, water or enemies, but that takes a bit more effort than simply being hit. However, as your plane is a superbeast, it repairs itself whenever you are not shooting.

Therefore, the solution to remaining on fire is getting shot and keep shooting.

And apparently, this "kill 50 enemies while on fire" fails to state that you have to kill the enemies by ramming them, while on fire. Embrace your inner fireball and get to work.