If you can handle the wind scenario and don't mind slow speed, you can run on electricity for a very long time (and have quite a large surface area to stick pan

If you can handle the wind scenario and don't mind slow speed, you can run on electricity for a very long time (and have quite a large surface area to stick panels on) which makes opex look attractive compared with heavier than air flight as well as being climate friendly. There's also probably an element of "Sergey Brin believes in it and he's not short of money..."