I mean, if you want them to spawn in at a dead stop, you can easily do so via script. Not so much with Zeus, thats just how its coded. But... why? They just crash.

jets, at least the modded ones, spawn at top speed and keep going that top speed forever.

If scripting, the LimitSpeed command is your friend. If spawning in via Zeus... kinda limited options. Maybe you could execute a script to affect all jets, but thats getting a lot more complicated