A friend (Larry P.) once suggested to me that he thought you could build a rural mobile phone much cheaper than Iridium network by putting nodes in all the airliners flying over the country. The airliners have power, and have line of sight to ground stations, and to a circle of about 200 miles radius around them. That’s pretty big (125,000 square miles) and in fact most locations will be within sight of an airliner most of the time. Indeed, the airlines already would like to have high speed data links to their planes to sell to the passengers, and relaying to people on the ground makes sense. It would not be a 100% on network, but that’s OK for many users. Phones would be able to warn about outages with plenty of advance notice to handle conversations, and indeed based on live computerized data from the air traffic control system, phones could even display a list of the times they would be connected.
I was thinking more about this in the context of InMarSat, which provides satellite services to ships and planes in the deep ocean. It uses geosynchronous satellites and auto-aiming dishes, but is quite expensive. Few people launch satellites to have footprints over the ocean.
Airliners fly so often these days, spaced often just 40 miles apart along the oceanic routes. It should be possible with modern technology to produce a mesh network that transmits data from plane to plane using line of sight. Two planes should in theory be able to get line of sight at 30,000 feet if they are up to 400 nautical miles apart. The planes could provide data and voice service for passengers at a reasonable price, and also could relay for ships at sea and even remote locations.
One can also use lower bands that can go further, since there is no spectrum competition over the the open ocean, but I suspect planes don’t spend too much time more than 400 miles from any other airliner (or 200 miles from any land station.) In the high bands many megabits of data bandwidth are available, and in theory spectrum allocation is not an issue when out of sight of land, so even hundreds of megabits would be possible. (We would of course not transmit on any band actually in use out there, and could even make a cognitive radio system which detects other users and avoids those bands.) An airline could offer just this service, or at a higher price switch to satellite in the few dead zones — which again, it should be able to predict with some accuracy. Aiming should be easy, since the aircraft all transmit their GPS coordinates regularly on transponder frequencies and can also do so in the data network. In fact, you would be able to know where a new mesh partner will be approaching, and where to point, before you could ever detect it with an omnidirectional antenna. And people could be given enough bandwidth for real internet, including voice. (Though that still means they should perhaps go to a phone lounge to have long conversations.)
Of course, I often find transoceanic flights one of the rare times I get work done without the distraction of the internet, so this could also be a terrible idea.
Some technical notes: Jim Thompson points out that doppler effects make this particularly challenging, which is an issue. I believe that since we know the exact vector of ourselves and the other aircraft, and we have many more bands at our disposal, this should be a tractable problem.