What would happen to the plane if people's mobile phones were on or someone was using their laptop?

Nothing.

One of the common sense evaluations that was done was to fly equipment (spectrum analyzers) to record what was going on in an aircraft during flight. They found that it was normal for one or two phones to be left on on a 737, people just forget. Absolutely nothing happens. So tens of thousands of flights have been completely unaffected by cell phones. One of my friends has sent text messages from a plane in flight.

Laptops don't emit much, in any case they are about to introduce 802.11 access on planes and the access points emit a lot more than laptops and they are still safe.

The story was that they were worried that a cell phone might bring down a plane, the truth was that they were worried a cell phone at 36,000 feet might be in contact with a lot of cell towers and cause problems for the network. There's the backup story that the license for cell phones to operate is ground to ground and you aren't allowed air to ground. Part of the issue with laptops is that if there is an emergency then they would be in the way, that's a good reason why you'll never be allowed to use them under 10,000 feet.

I work for one of the companies putting WiFi in aircraft, we have done trials and there is absolutely zero modification to the aircraft systems. They just add a couple of Ethernet cables to reach the access points and provide power over ethernet (802.3af) to the access points. We sent one guy with two APs to support the demo. No problem what so ever.

Why is it people don't want to believe the facts?

2

Nothing. Neither cell phones nor laptops are likely to interfere with aircraft avionics.

However, air regulations require that airlines not allow the use of electronic devices unless they have been determined to be safe, and since most airlines don't want to spend the time or money to prove that cell phones or laptops are safe, they simply prohibit their use during all or part of the flight.

Cell phones also cannot be used on flights in the U.S. because there's an FCC regulation against it. Contrary to a widely-held misconception, there's no Federal air regulation against using cell phones specifically (beyond the generic restrictions above).

Big myth. I travel all the time, never turn off my phone. I don't use it while in flight, as there is no reception typically. I would imagine if everyone on board had a cell phone and didn't turn it off, it may cause some static for the navigator, but not an issue.

It's ok to use your laptop or cell phone anyway, when the crews says is ok to do so. Usually after take-off and before landing. Just not wi-fi or bluetooth. On all cell phones, the ability to broadcast must be disabled. Even when you;re not making a call, the phone is looking for cell towers, and sending signals. So the phone must be set to flight or airplane mode (or turned off completely).

Flights are being equipped in a few airlines to allow internet access. These flight have a built in network, and specially shielded electronics and wiring.

Cell phones not in flight/airplane mode do interfere with communications. My wife has had to board aircraft and remove passengers who have refused to hang up and turn off their cell phones. They knew it was happening because the pilot heard the unique static that a cell signal generates though their headsets.

Everytime someone asks this, I suspect they are thinking of just their little old cell phone. Uh uh. More like dozens and dozens of cell phones in use, lots of signals interfering.

Supposedly it can interfere with the planes electrical systems, which could mess up navigation and/ or communication. So that could be an issue.

In general, I don't think there's much risk, and eventually, there'll be internet allowed on planes. But it's a better safe than sorry policy to have electronics that could possibly interfere turned off.

planes need to be in constant communication with the ground, and are constantly squawking (sending of signals) and they worry mobile phone signals interfere with that, also they cant risk any emergency message, either being received by the plane, or being sent by the planes computers to be interfered with. additionally they are believed to interfere with the planes readings, odometer, altimeter and so on. chances of these things happening are slim, but in the aviation industry, chances cant be taken.

not only laptop/cellphones, handheld videogames (ie gameboy, etc) can also interfere aircraft navigations/control (since, many aircraft uses digital flight controls/ fly by wire) . Some incidents said that the commercial passenger aircraft moves in a very slow/slow yaw or roll, so pretty/dangerous. Although the technology nowadays allow some airlines to allow their passengers to operate their digital devices.

Aircraft acutally provide free internet, urging you to use laptops...

Wires are so hard coated with anti interference, that nothing would happen to them...

But hey, you can always take your chance

nothing would happen.

With on average some 150 people on board any airliner and 50% of those forgetting to turn their cellphones off (my guestimate, based on how often I forget it), that's on average 75 working cellphones on any one airliner that's in the air at any time.

None of them suffer any failure because of that.