It appears that plans for long duration unmanned lighter than air surveillance platforms continue apace, with a subscale demonstrator, the High Altitude Long Endurance Demonstrator (HALE-D), due to fly in August. (paid subscription required)

This aircraft, which relies on solar cells and batteries to maintain station for 2 weeks at 60,000 feet altitude with a 50 lb sensor payload, with successor operational aircraft extending both payload and range significantly, though they would be huge, as this demonstrator is already twice the size of the Goodyear blimp.

Me, I’m dubious of the return of the airship, if just because takeoff and landing are so troublesome in anything but absolutely calm weather.