Using Luftansa's wireless broadband service, Apple product line manager Eric Zelenka videoconferenced with a coworker in Cupertino on the way back from Munich:
Although the wireless Internet connection involved sending data from a Boeing 777 traveling at 500 mph through a satellite receiver in a 20,000 mile earth orbit, conferencing with Zelenka was as easy as clicking his video status button.
Between cheap mobile technology, WiFi, Bluetooth, and software that takes advantage of all that, you've got a scenario where 2 or more people on the same plane can have stealth conversations with each other, possible on-ground coordinators, and even people on other planes, working together to plan and execute hijackings. Someone could be iChatting away to a cohort in 23C without his neighbor suspecting anything was up, sharing notes on the likely positions of onboard guns (armed air marshals are easy to spot) and coordinating their plan of attack. I'm wondering how distant we are from the day when all electronic devices will be banned from commerical flights.