By Chris Stonor
If you have time, please read through this extensive study/survey carried out by the Stuttgart, Fraunhofer Institute for Industrial Engineering. It is headed by Sebastian Stegmuller and Franziska Braun in co-operation with Volocopter. Well worth a perusal.
http://publica.fraunhofer.de/starweb/servlet.starweb?path=urn.web&search=urn:nbn:de:0011-n-6059702
