Using your jumpjet to get in to a vehicle causes it to constantly be used whilst you're inside the vehicle. It's as if someone on foot was holding down space - it'll go all the way down, charge up a couple of bars, go back down, etc. I first noticed this when I jetted up in to a liberator, then tried to drop down in to a base.. only to realise my jumpjet was out of fuel. The same happened with a sunderer, so I'm pretty sure it's not a one-off glitch. In case it makes a difference, I play VS.
