There could be jetpacks in the game, since they don't give any great advantage to their users. Jetpacks are not poweful vehicles like Hydra and Hunter, nor extreme weapons like bazooka and flamethrower, so they wouldn't allow any noob casual to abuse of their power and ruin the game like the mentioned vehicles and weapons. Unless there's any bug, a flying player is almost as vulnerable as someone on the ground: although he is flying, he can still be shot at (since jetpacks cannot reach a big speed nor alttitude), and the only weapons he can use to counterattack are Tec9, Uzi or MP5, and he can't use sawns nor AK47 while he's using jetpack, so he wouldn't be too destructive to ruin the game. Besides, he would be more vulnerable to helikilling and also an easier target to Rustlers. Additionally, controlling the jetpack while you try to aim your weapon is quite challenging...
And even in the case jetpacks gave a true advantage to their users, if they were available to everyone the game would be balanced again...
Besides,
can you imagine how amazing Ammunation and LVPD wars would be if there were lots of players flying around up and down?? It would be awesome!!!
Maybe some of you know a shooter called Section 8.
And of course an air combat of jetpack vs Rustler would be very interesting too...
One or two admins told me the other day that cheaters couldn't be detected if everyone were using jetpacks... well, if jetpack is now a cheat, it's just because they aren't enabled. However if they were, using one wouldn't be a cheat. Besides, if the system can detect money cheaters, weapon cheaters, health cheaters etc. it would also be able to detect those theoretical jetpack cheaters.
I was also told something about jetpacks being invulnerable... is that a bug? because in normal conditions it should be possible to shoot them. Well, if they are really invulnerable, then you can forget about this suggestion, but if they aren't, you should think about it.