To assist the Marines

Here is a video of the F35B making its first vertical landing at sea. "The F-35B is the variant of the Joint Strike Fighter for the U.S. Marine Corps, capable of short take-offs and vertical landings for use on amphibious ships or expeditionary airfields to provide air power to the Marine Air-Ground Task Force."
Found here: http://www.blackfive.net/main/2011/10/the-first-f-35b-landing-at-sea-on-the-uss-wasp-1.html

(link provided by Instapundit)