Originally Posted by studentff
1) The ban on cell phone use is a Federal Communications Commission (FCC) regulation, not a Federal Aviation Administration (FAA) regulation. That is an important detail. The FCC did not want people using old-style analog cellular phones at altitude because their signal would reach many different towers and clog the network. The airlines had little motivation to test their planes for cell-phone interference because the phones were banned by the FCC. Now that the airlines have some such motivation (new digital phones don't have the same problem, relaxed on-the-ground rules, plans to sell in-flight cell service), the airlines seem to be finding cell phone use quite safe.
IIRC, there was another problematic issue with cell phones, one that doesn't go away with digital phones -- the cell networks aren't designed to handle the rapid handoffs between cell towers that would occur at cruising speeds. At least at one point, there was a significant concern that having lots of cell phones continously being handed off between cells at a fast pace would overwhelm the system and disrupt service for everyone.
Originally Posted by studentff
2) Most "evidence" of personal electronics causing actual interference on flights is extremely anecdotal and difficult/impossible to repeat in a lab. At one extreme, such interference may be completely myth.
I thought your seat belt analogy was very appropriate. Similar reasoning undoubtedly applies to the various IFE systems on board planes -- a video system isn't very likely to cause interference, but multiple the total number of on-board systems by the number of flights per day and a miniscule risk can suddenly become an inevitability; hence, the thorough testing of all on-board system prior to deployment. Also, it doesn't take much of a "glitch" at certain critical points in a flight to cause a serious problem (e.g. mid-air collision, missed approach, etc.).
Another aspect of the problem is that cell phones tend to generate a much stronger signal when searching for service. Essentially, they keep increasing the power up to their maximum as long as they don't detect a signal. At 30,000 feet, there's little, if any, signal to detect, so phones have a much greater potential for interference. On the ground at airports (where airlines now permit usage), signals are likely to be quite strong and thus there is generally lower signal output from cell phones.
The proposed on-board systems address both of the concerns mentioned here: the on-board "cell tower" is obviously very close to the passengers, which provides a strong signal and hence lower power output from the individual phones. This in turn greatly reduces any chance that the phones' signals could possibly reach a tower on the ground, so the rapid handoff problem goes away. The on-board cell tower uses a completely separate link (satellite, I believe, rather than the usual cell frequencies) to relay calls to/from the ground.
AFAIK, the real problem now is not the technology -- it's the human factor. Airlines are concerned that passengers will not deal well with being trapped next to a chronic cell phone user for several hours, particularly in cramped economy seating. At several dollars per minute with today's on-board phones (ok, even at the $0.69 / minute discount Airphone rate for Verizon subscribers), there aren't too many people who make any calls, much less long ones. Receiving calls, where possible, is even more of a hassle. But once pax can use their own phones and potentially pay much lower rates, the potential is there for a plane full of people with cell phones glued to their ears for a 5-hour transcon flight.