Wikipedia has this to say about it:
"...the primary reason for the ban on cell phone use in flight is that neither the FAA nor the FCC are willing to spend the money to perform conclusive safety tests. They have left this up to the airlines
who do not see any return on investment made in paying for such tests."
If airlines charge extra to transport your bag or give you a glass of coke instead of the whole can everybody screams bloody murder. Just imagine what happens if airlines increase their ticket prices to cover the costs of testing consumer electronics for interference with flight systems, or for building a shielded compartment for eAddicts.
The costs would be pretty high, because the distance between a phone and the nearest cell tower will never be less than the altitude of the plane, i.e. a phone aboard a plane will always transmit at maximum power, whereas a phone on the ground will rarely need to do so.
Of course electromagnetic shielding can be done. Put some seats in a sealed compartment and charge pax in the new iClass-of-Faraday $100k o/w for the privilege of texting their girlfriends and a few extra minutes of laptop time between the ground and 10k ft.
It's reasonable to assume that statistical analysis by NASA and testing by IEEE is more reliable than the gut feeling of passengers who can't survive a few hours without their Blackberries, so let's look at the data.
The results of a NASA study on interference by cell phones and laptops:
Originally Posted by http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010066904_2001108092.pdf
A compilation of data on personal electronic devices (PEDs) attributed to having created anomalies with aircraft systems. Charts and tables display 14 years of incidents reported by pilots to the Aviation Safety Reporting System (ASRS). Affected systems, incident severity, sources of anomaly detection, and the most frequently identified PEDs are some of the more significant data. Several reports contain incidents of aircraft off course when all systems indicated on course and of critical events that occurred during landings and takeoffs. Additionally, PEDs that should receive priority in testing are identified.
These were incidents from 1986 to 1999. Since then the use of personal electronics has grown exponentially, so it's reasonable to assume that the number of incidents and their associated risks has grown accordingly.
From the IEEE:
Originally Posted by http://spectrum.ieee.org/aerospace/aviation/unsafe-at-any-airspeed
All in all, we found 125 entries in the ASRS database that reported PED interference. Of these, 77 were considered highly correlated, based on the description of observed PED use and interference occurrence. The reports included cases of critical aircraft systems such as navigation and throttle settings being affected. Based on the random sample entries from 1995 to 2001, we estimate that the average number of reported interference events might be as high as 23 per year.
[...]
In one telling incident, a flight crew stated that a 30-degree navigation error was immediately corrected after a passenger turned off a DVD player and that the error reoccurred when the curious crew asked the passenger to switch the player on again. Game electronics and laptops were the culprits in other reports in which the crew verified in the same way that a particular PED caused erratic navigation indications.
Banning cell phones became popular after the Crossair crash in 2000 which killed ten people. The autopilot malfunctioned at the same time one passenger received a call and another one received an SMS. That's no conclusive evidence, but it's a good reason to be safe rather than sorry and to put the burden of proof on those who want to use their phones and laptops instead of on those who want to ban them.
Originally Posted by ralfp
If cell phones, etc. can interfere with avionics, we should blame Boeing, Airbus, the airlines, etc. for manufacturing/operating aircraft that are unsafe in the presence of devices that will most certainly be active during takeoff & landing.
Most planes currently in service were built way before everyone was running around with phones and laptops and iPods. Phones and spinning hard drives (the number two source of interference) were not an issue in airplane design, just like the future inventions of 2020 are not catered for in airplane design today.
Maybe the phones and laptops of 2030 won't ever be charged again because they contain a tiny little nuclear power source that keeps the device running until you die of old age. Should Airbus and Boeing already adjust the design of their planes because such a scenario might become reality? The technology in the planes flying around today dates from a time when nobody anticipated that cell phones would outnumber people.
The first iPod hit the market in 2001. Your average airplane is older than that. Back then most people did not use cell phones.
Originally Posted by Takire
I am pretty sure out of 100 or 200 passengers, there a couple of souls with their mobile phone on. I guess this is the case for most flights...and guess what...nothing bad happens.
Managing risks is not an all-or-nothing game. On any given highway there are one or two drunk drivers, but they usually manage to complete their drunken trip without killing anyone. This is no reason to allow DUI, because then roadkill would turn from small chance to near-certain likelyhood.
The same reasoning applies to cell phones in planes: the risk of having one live phone aboard is small. Let's keep it small by not letting all 300 passengers yap away in mid-air.