One of the coolest bits of technology in Marvel's "The Avengers" and "Captain America: Winter Soldier" are S.H.I.E.L.D.'s helicarriers. Aircraft carriers are already amazing technological achievements, so a flying one would be that much cooler.
If you haven't seen the movies, here's what I'm talking about:
In the real world, a helicarrier would have lots of drawbacks like tremendous cost, complicated flight systems, vulnerability to enemy fire and bad weather, and the physics of getting that much metal to stay in the air. Still, that hasn't stopped DARPA from thinking in that direction.
Specifically, DARPA wants a flying aircraft carrier for drones. Drones tend to have limited range, so a larger vehicle that can get them near the action and recover them for the journey home isn't a bad idea.