for airplanes take-off

this is also a possibility

Given that the DRAE gives this as an abbreviated version of autopista, I would think that your first option was the most likely (unless the rest of the text indicates otherwise). However, if you can't ask the client what is meant exactly (which would be the easiest option), and given that pista can mean many diferent things, you could at least add a translator's note saying that you have assumed it was a highway, but if not the other options would be ... and list them.
This is what I would do.

you're right. I could be anything, from runway to speedway, racing track, jogging track, go-kart track