That ringing sound you hear on your next flight to Mexico may well be someone calling your cell phone. The Mexican government has ended an eight-year ban on the in-flight use of cell phones and Aeromexico, Mexico's largest airline, said it will permit the use of cell phones on flights over Mexican territory.

Cell phone use is "prohibido" on U.S. flights, but as the practice gradually gains hold in global markets, supporters believe it is just a question of time before cell phone use comes to U.S. flights.

Mexico's relaxation of the rules isn't completely wide open, however. Flight attendants and pilots will monitor the use of the phones and can authorize their use at specified times. They can also order phones to be silenced if they become a nuisance.

The Mexican government lifted the ban after it discussed the issue with passengers, flight safety experts, pilots and flight crews. In the U.S., flight crews in particular have opposed the use of cell phones.

As U.S. airlines -- under pressure to boost revenues -- have been installing Wi-Fi equipment on their passenger jets, cell phone usage could represent a new source of revenue. At present, voice calls are blocked, including VoIP calls over Wi-Fi connections.

In Europe, in-flight cell phone use is not only widely tolerated, it is in demand by most passengers. The service is provided by OnAir, which has estimated the service will be used on more than 100,000 flights by the end of the year.

"The feedback from in-flight experience shows that phone use inside aircraft does not create any discomfort to passengers," OnAir CEO Benoit Debains said recently. "We have not had one single complaint."

The feeling is different in the U.S. where Congressman Peter DeFazio (D-OR) has spearheaded a drive to keep U.S. commercial flight free from passengers talking on phones. "However," he said recently, "with Internet access just around the corner on U.S. flights, it won't be long before the ban on voice communications on in-flight plans is lifted."

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