Could my cell phone really bring down a plane?

Answers to your questions about the news.
March 31 2009 7:10 PM

Could My iPhone Really Crash My Airplane?

What about an onboard Wi-Fi network?

Commercial plane flying with sunset. Click image to expand.
Is using a cell phone aboard an airplane really dangerous?

American Airlines announced Tuesday that it will expand in-flight Wi-Fi Internet service to its entire fleet. The airline, along with Delta and Virgin America, started offering Wi-Fi on select planes in late 2008. In-flight calls, however, are still prohibited. If I can surf the Web, why can't I use my cell?

It operates on a totally different frequency. Cell phones transmit signals at roughly the same frequencies as aircraft communications—pilot radios and radar range from below 100 to 2,000 MHz, and many phones operate at 850 MHz or 1,900 MHz. Your cell could therefore—at least theoretically—interfere with navigation. Wi-Fi, on the other hand, signals at a higher frequency—anywhere from 2,500 to 5,000 MHz—and thus won't get mixed up with the plane's transmissions.

In-flight Wi-Fi works like a moving Starbucks hot spot. The plane is rigged with three antennae—two on its belly and one on top—that receive signals from towers across the country. The frequency of those transmissions, 849 MHz, is within the range of airline communications. But they don't interfere with the plane's navigation, since 849 MHz is a dedicated frequency that was auctioned off and bought in 2006 by Aircell, which services American, Delta, and Virgin. (It's the same frequency once used by Airfone.)

But are cell phones on planes really that dangerous, anyway? Studies analyzing the dangers of in-flight cell-phone use suggest the risks are small but real. In 2003, a study by IEEE Spectrum concluded that "continued use of portable RF-emitting devices such as cell phones will, in all likelihood, someday cause an accident by interfering with critical cockpit instruments such as GPS receivers." A study produced by the Radio Technical Commission for Aeronautics in 2006 found that portable electronic devices can interfere with airplane communications and laid out testing guidelines for airlines to figure out which devices should be permitted.


The rationale for switching off other portable electronic devices is slightly different. Even if a device doesn't transmit a signal—think iPods, Game Boys, "anything with an on-off switch"—it still emits energy at a frequency that could, possibly, interfere with the plane's electronics. The Federal Aviation Administration requires all such devices to be off during takeoff and landings, but you're allowed to turn them on once you reach a cruising altitude—presumably because any interference would be minimal and temporary. There are exceptions, though, for necessary devices like hearing aids and pacemakers.

Some international airlines do allow cell-phone use. Emirates Airline permits in-flight calls as long as you use an onboard picocell network, which isolates the cellular communications from the pilot's. In the United States, the resistance to in-flight calls is strong, but often for social rather than safety reasons. Members of Congress have even introduced legislation to keep cell phones off planes, titled the Halting Airplane Noise To Give Us Peace Act, or HANG UP Act.

Christopher Beam is a writer living in Beijing.



The World’s Politest Protesters

The Occupy Central demonstrators are courteous. That’s actually what makes them so dangerous.

The Religious Right Is Not Happy With Republicans  

The XX Factor
Oct. 1 2014 4:58 PM The Religious Right Is Not Happy With Republicans  

How Did the Royals Win Despite Bunting So Many Times? Bunting Is a Terrible Strategy.

Catacombs Where You Can Stroll Down Hallways Lined With Corpses

Homeland Is Good Again! For Now.


Operation Backbone

How White Boy Rick, a legendary Detroit cocaine dealer, helped the FBI uncover brazen police corruption.


How Even an Old Hipster Can Age Gracefully

On their new albums, Leonard Cohen, Robert Plant, and Loudon Wainwright III show three ways.

The One Fact About Ebola That Should Calm You: It Spreads Slowly

Piper Kerman on Why She Dressed Like a Hitchcock Heroine for Her Prison Sentencing

  News & Politics
Oct. 1 2014 6:41 PM The World’s Politest Protesters The Occupy Central demonstrators are courteous. That’s actually what makes them so dangerous.
Oct. 1 2014 2:16 PM Wall Street Tackles Chat Services, Shies Away From Diversity Issues 
Oct. 1 2014 6:02 PM Facebook Relaxes Its “Real Name” Policy; Drag Queens Celebrate
  Double X
The XX Factor
Oct. 1 2014 5:11 PM Celebrity Feminist Identification Has Reached Peak Meaninglessness
  Slate Plus
Behind the Scenes
Oct. 1 2014 3:24 PM Revelry (and Business) at Mohonk Photos and highlights from Slate’s annual retreat.
Brow Beat
Oct. 1 2014 6:39 PM Spoiler Special: Transparent
Future Tense
Oct. 1 2014 6:59 PM EU’s Next Digital Commissioner Thinks Keeping Nude Celeb Photos in the Cloud Is “Stupid”
  Health & Science
Oct. 1 2014 4:03 PM Does the Earth Really Have a “Hum”? Yes, but probably not the one you’re thinking.
Sports Nut
Oct. 1 2014 5:19 PM Bunt-a-Palooza! How bad was the Kansas City Royals’ bunt-all-the-time strategy in the American League wild-card game?