The Economist on how airborne Wi-Fi works:
…another firm, now called Gogo, purchased a thin sliver of air-to-ground spectrum in the United States, and began service in 2008, deploying dozens of ground stations that point upwards at aircraft, rather than downwards at people on the ground, and use a variant of 3G mobile-data technology called EV-DO
Slightly technical, but really interesting explanation on how the Internet becomes airborne. I assumed it was all via satellite, which is why I could never figure out why it would never work over the ocean. Turns out most of it in the U.S. is based on ground-to-air links: instead of pointing cell towers towards people on the ground, they’re pointing them towards the sky.