I've been trying to beat Mission 4, Arcadia City, on Legendary and I just can't do it. No matter what, something always happens. I did co-op with my friend and we got down to 5 seconds, then all of a sudden Cargo 2 blows up. Kind of happens all the time too. I watch the cargo ship as it has full health, then it just drops to nothing. It doesn't even gradually drop, so I'm kind of stuck here..

First thing u wanna do is let one of the cargo's get destroyed, that gives u the choice to build a base, and looking after 2 ships is alot easier than 3.

Get as many tanks as u can, place about 4 or 5 in a circle around each ship and a few along the path that the civilians take to get there.
A fleet of hornets is a good idea too, to get places quickly in case of an emergency.


Also, use your healing power thing on the ships if they get damaged.