An aircraft generally sorties already knowing what its mission is. So, dynamic elements of such a mission should focus on things that occur unexpectedly.
I would rule out most strike and convoy/fleet defense missions based on this. However, you might respond to transiting subs being detected by SOSUS nets while transiting, protecting a downed pilot from surface threats, locating a vessel suspected of piracy.
Another way to work in something dynamic might be to have to track a detected sub contact, and to have the mission objectives based on what the sub does (i.e. tracking on a certain course indicates no threat, while another sub might be positioning for an attack and is declared hostile). Subs transiting to certain areas might give hints about an adversaries strategic objectives, which might call for a time-sensitive recon mission as well.
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