I saw this article and thought about the blimp. This thing can stay aloft for days and can be configured to carry 10 tons of cargo or 48 passengers. It also says it can go 92 MPH. Looks like it has 'Modules' for different applications.
Airlander 10
http://www.cbsnews.com/news/airlande...t-test-flight/
It could carry multiple ultralights quite easily.