Equatorial wind speed at 60,000 feet?
Google is buying Titan Aerospace, a company which plans to make solar-powered drones that can loiter for up to five years (they say, six months is probably more like it) at a target altitude of 60,000'. Google says that it's interested in this for, among other things, bringing broadband to developing countries.
A quick look at the specs for these beasts says that they will be able to do around 65 mph. Which doesn't sound much... but apart from the small business of getting up and down safely, is that enough for station keeping for months at a time at that altitude over, say, Africa?