Personally, I have always considered the missile to act like a Skimmer. That is, it can pass over any terrain as needed to reach it's target. It can also choose to go around said terrain if the player needs to use up distance or does not want to risk getting Snap Fired upon.
However, there could be benefit to defining the missiles as Flyers. Then they could travel at High altitude and thus target other Flyers at that altitude.
Either way, it should be specified. Or not.
@scream: your wording just above is decent. I would change it slightly to:
Quote:
In the turn that the missile is launched, it is placed 35cm directly in front of the launcher. It ignores any and all terrain and models between the launcher and the 35cm point, as it takes that time to briefly rise to "High Altitude" to locate targets. If any legal target(s) are at this point, the player may choose to detonate the missile immediately. If it is not detonated at that time, it must move 35cm in each turn in which it does not detonate, and may move up to 35cm in the turn in which it does detonate. This movement happens during the Compulsory Movement Phase. During movement, the missile acts as a Skimmer except that it cannot perform a 'Pop-up'.
Note the difference between "must" and "may".