[Fate]

Yes. Your stealth unit will arrive to the battle.

Normal movement (of any kind) happens before normal battles, so you shouldn't need to worry about this. The only time you need to worry is magic battles and assassinations and sneak attacks (which happen before movement). Magic attacks (which include teleporting armies) and assassinations and sneak attacks are the only three things that can intercept armies.

A flying army cannot be intercepted unless the commander(s) is(are) killed (by assassination or because they were killed in a pre-movement battle).