Early Sept. 11, airline passengers all over the country boarded their flights like any other day. Many chatted on their wireless phones. As the doors closed and the pilots prepared the planes for take-off, flight attendants asked passengers to turn off their wireless phones until the planes had landed at their destinations.

But on four flights, these phones would offer the last contact passengers would have with their loved ones. They would be using their wireless phones to say goodbye.

Later that morning, thousands of stunned people working at or near the World Trade Center's twin towers in New York City also reached for their wireless phones to call family and friends after the two buildings had been attacked by commercial airplanes. The fortunate ones were able to reassure loved ones that they had made it out of the buildings safely. The others made their last calls.

The use of wireless phones during the attacks already has caused some unexpected changes. AT&T Wireless, Nextel and Verizon Wireless all reported increases in wireless-handset sales immediately following the attacks, perhaps due to heightened safety concerns. But will the importance of wireless phones during this tragedy spur other changes as well?

Calling From 30,000 Feet

Because wireless networks are designed for terrestrial use, the fact that so many people were able to call from the sky brings into question how the phones worked from such altitudes.

Alexa Graf, AT&T spokesperson, said systems are not designed for calls from high altitudes, suggesting it was almost a fluke that the calls reached their destinations.

“On land, we have antenna sectors that point in three directions — say north, southwest, and southeast,” she explained. “Those signals are radiating across the land, and those signals do go up, too, due to leakage.”

From high altitudes, the call quality is not very good, and most callers will experience drops. Although calls are not reliable, callers can pick up and hold calls for a little while below a certain altitude, she added.

Brenda Raney, Verizon Wireless spokesperson, said that RF signals actually can broadcast fairly high. On Sept. 11, the planes were flying low when people started using their phones. And, each call lasted 60 seconds or less.

“They also were digital phones, and there's a little bit more leeway on those digital phones, so it worked,” she said.

It helped that the planes were flying in areas with plenty of cell sites, too. Even United Airlines flight 93, which crashed in rural Pennsylvania, was supported by several nearby cell sites, Raney added.

Despite the numerous calls from wireless phones, it was the hijackers — not interference with the airplane's operating system — that brought the four planes down. Many in the wireless industry question whether wireless devices cause problems on board aircraft after all.

“With air travel, you want to take every precaution you can, but my understanding is that not calling from planes is a bit of a precaution,” Graf said.

Keith Nowak, Nokia media relations manager, agreed.

“In reality, a cell phone could cause a warning light not to work, but it wouldn't be anything serious. There's the potential to cause some effects, but it's generally a preventative measure.”

Change Unlikely

Following the attacks, Northjersey.com reported that the FAA is rethinking the ban on cell phones while flying. However, it looks as though any change is unlikely.

“Practically the entire spectrum of options for improving safety and security are being looked at in the wake of the Sept. 11 incidents, but I can't speculate on whether or not one would be to authorize the use of cell phones in an emergency, especially because there's evidence that cell phones can interfere with critical systems,” said Les Dorr, FAA spokesperson.

Dorr emphasized that the rules prohibiting wireless-phone use while flying is not actually an FAA prohibition, but an FCC restriction. The FAA supports that restriction because it's possible that wireless phones could pose a source of interference to critical aircraft systems.

“FAA regulations prohibit any device that is an intentional emitter of radiation, which a cell phone obviously is,” he added.

According to an advisory on the FAA Web site, the FCC currently prohibits the use and operation of wireless phones while airborne. Its primary concern is that a wireless phone, while used airborne, would have a much greater transmitting range than a land mobile unit.

“This could result in serious interference to transmissions at other cell locations since the system uses the same frequency several times within a market,” according to the advisory. Because a cellular mobile telephone is capable of operating on all assignable cellular frequencies, serious interference also may occur to cellular systems in adjacent markets.

Harter (betsyharter@aol.com) is a freelance writer based in Athens, GA.