You board the plane, sit down, and are talking to someone on your phone. Maybe you're talking to a loved one. Maybe you're talking to your boss. The flight attendant comes by and asks you to turn off your phone. For more than one reason this is a reasonable request. But if you ask, "Why?", you are told that it could interfere with the communications in the cockpit. Most people just accept this and comply. Tek saavy folks regard this claim as totally idiotic.
First of all, the Federal Aviation Administration (FAA) does not exlude all Personal Electronic Devices (PED's), such as voice recorders and pacemakers. However, they do stipulate that all other PED's be powered off below altitudes of 10,000 feet because the Federal Communications Commission (FCC) is the one calling the shots. There are some very good reasons for this far-reaching rule. Here are the facts:
When you travel from one cell tower to another, a "Hand-Off" occurs. At this point, your phone changes radio frequencies without you knowing it. Code / Time Division Multiple Access (CDMA, TDMA) structures are known to be "soft" and Global System for Mobile Communications (GSM) are known to be "Hard". It's all in the name. CDMA (Verizon and Sprint) frequencies are shared, whereas GSM (AT&T and T-Mobile) use dedicated frequencies. Both have their benefits and downfalls. Using a CDMA phone on the freeway will (almost) always ensure a service interuption free conversation, but you might hear someone else's converstation in the process (or feedback). With GSM you (probably) won't get any of the clutter but might get dropped because the switch between your phone and the tower may not take place as rapidly as needed. Why does this matter when you're on an airplane?
Cell towers transmit frequencies in wattage according to area/usage. The average altitude ceiling for such radio waves is about 8,000 feet. The problem occurs when you try to make a call and the towers are trying to switch as fast as your are traveling (below 10K feet it ranges from 140-250 kts.). At these speeds, your frequency is used among multiple towers. If you are able to connect with the tower, it is designed to send out a burst of wattage to keep you connected. This wattage burst and sharing MIGHT cause a tower network to become unstable, which is bad for terrestrial users. The fact is that over 10K feet, you will probably be unable to connect your call. In no way does this interfere with cockpit transpondance. Why? Because aviation VOR/COM systems communicate between 2.8-3 khz (High Frequency), 108-136 Mhz (VHF), and some between 136-156 Mhz
The average cell phone cooresponds on a frequency range of 1700-1900 Mhz. The FCC prohibits (free) public transmission usage between 700-850 Mhz on airplanes because these are frequencies dedicated to companies that license in-plane cell service. The frequency happens to be one of those "Citizen Bands" but with greater consequence. The fact is that these frequencies have a stronger amplitude and are given a much larger wattage allowance and are able to reach a plane at higher altitudes. Think of it like this: You can hear the car with bass better than you can one filled with tweeters. Why? Because low frequencies penatrate easier. You're CDMA 4G phone (Moto Droid X) falls right into this category. However, there aren't any restrictions for private aircraft and PED's that use these systems. GPS communication systems operate on 1.2 Ghz and 1.5 Ghz. The worse that will happen (on smaller unsheilded crafts) is that the pilot will hear static over the speakers when your phone rings, at which point you will be told to shut up and enjoy the ride.
What about Wifi? Normal consumer electronics are usually 2.4Ghz and 5Ghz and far beyond the GPS spectrums and VOR/COM/Radar transmissions. I want to also point out that commercial aircraft sometimes have microwave ovens, which are known to interfere with WiFi transmissions. If the Microwave oven doesn't interfere with communications, neither will your laptop/phone.
There are have been reports of interference due to PED's while in flight. The FAA and FCC have even gone so far as to purchase the offending phone and test it. The main problem I've seen is that the FAA forbids testing of VOR/COM systems while airborn, so these tests were performed on the ground and the results have NEVER been duplicated. It is entirely possible that a PED could cause interference, but without duplicating the exact conditions (altitude, speed and geography), it's impossible to be prove causation. In fact, there have been numerous tests where planes were bombarded with high wattage signals and not one of them was conclusive.
Now that we know that it is improbable that a simple PED could cause any type of interuption between Air Traffic Control (ATF) and a commercial transponder, let's talk about the reality of the situation.
When cell phones started proliferating in the 1990's, many people talked on their phones because it was a status symbol. "Look at me! I'm on a plane AND I'm talking to someone"!!!! I know it sounds stupid now, but it was true. These people would run their mouths and annoy everyone around them, just as they do today. Because it was a status symbol, people were in fact paying attention to them and not the flight attendant trying to give out instructions in the case of a water landing. Grandma was freaking out because she's afraid of flying and Talky McMouth is adding undue stress. Instead of telling the passenger to STFU because it's annoying, they took a safety/fear approach. "There are electronics in the cockpit and one in your hand. That phone could interupt everything and make us crash. You don't want to die, do you"? Think about it, before reading this article did you know what frequencies are used for airline communications? So, this argument seems logical because the average person lacks critical thought. The point is this.
The FCC does not want you to use your phone on a plane because the higher you get, the more likely it will interfere with ground based cell systems/devices. The FAA doesn't want you talking on the phone during the most critical times of flight. Talking on the phone increases the chance of Air-Rage.
Turn off your stupid phone on an airplane. There is no reason to use your laptop/tablet because whatever you need to do can wait a few minutes. The most dangereous period of flying is landing and planes hit air-pockets all the time. When they ask you to wear your seat belt, do it. There are two things that are unneeded during ascent/descent.
1. People flying around the cabin because they weren't wearing their seat belts
2. Electronics flying around the cabin because they weren't secured.
This is all very much about death and injury. In these post 9/11 days, where a bottle of water isn't allowed through a security check point, why would they ever allow anything on a plane that could possibly bring it down? They wouldn't. However, explaining the actual reasons requires an article and the flight attandents don't have the time or resources to explain it every time.
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