We carried out extensive aerial survey work in Yemen a few years back and although we never had occasion to land there we did research it in the event of needing to.. it's come a long way since I had to avoid it back in my professional sailing days (pirates)... I think that it's pretty safe now... there's a company there that should be able to help you out.. I think it's called International Air Charter Socotra... They do definately have Jet fuel available though like all islands deliveries can be spasmodic so advance arrangements will pay off... on the down side you're not likely to find a beer there so take your own and... it's home to the worlds deadliest spider.