One of airline travel's least-cherished rituals — powering down electronic devices before takeoff and landing — is coming to an end. Here's what travelers need to know:

1What's in: The FAA initially will allow smartphones, tablet computers and MP3 players to stay on throughout flights, including during takeoff and landing phases, if they're set to so-called airplane mode, which turns off cellular connections. To surf the Web, download content or play online games at altitudes below 10,000 feet, their flight will have to be equipped with a Wi-Fi service designed to work during those phases. Heavier devices will have to be stowed.

2 What's out: Mobile-phone calls and text messages will remain forbidden at any time during flight. They are separately banned over concerns that the signals may interfere with ground networks.

3 The timing: The speed of the transition will vary by airline. Airlines will have to show the FAA that their airplanes meet the new guidelines and that they've updated their flight-crew training manuals, safety announcements and rules for stowing devices to reflect the new guidelines.

However, Delta Air Lines and JetBlue Airways Corp. announced that they became the first airlines to allow passengers to leave their electronics powered up during flights. Delta allowed its domestic passengers to stay logged on. JetBlue has qualified its entire fleet for passenger electronics during all portions of flights, it said. JetBlue, which doesn't offer its passengers Wi-Fi, is planning to add that service on some planes by the end of the year, Jenny Dervin, a spokeswoman, said.

American Airlines said it has started the process of asking the FAA to approve broader device usage. Smaller, regional jets might take until the end of the year to certify.

4 Why it's happening: The guidelines reflect the evolution in types and prevalence of devices used by passengers over the past decade. In 2003, 70 percent of passengers carried electronic devices with them on planes, and the most common device was a cellphone that wasn't capable of connecting to the Internet, followed by a calculator, according to a survey by the Consumer Electronics Association. A follow-up survey by the association this year found that 99 percent of passengers carry some device with them, with smartphones the most common followed by notebook or laptop computers. Allowing broader use of onboard electronics will help Amazon.com, as Kindle owners may have more time to buy and download content, as well as Qualcomm Inc., which won preliminary regulatory clearance in May for an air-to-ground broadband service. "This is a big win for customers and, frankly, it's about time," Drew Herdener, an Amazon.com spokesman, said.

5 Caveats: It will be important for passengers to stop using devices and pay attention during the safety briefing before each flight, FAA Administrator Michael Huerta said. And he urged passengers to heed instructions from flight attendants since devices allowed on one fleet of aircraft may be prohibited on another.

6 What's next? Other nations are likely to follow the FAA's footsteps. Britain's Civil Aviation Authority said it welcomed the FAA's move, noting that electronic devices were a fact of modern life and "naturally passengers want to use them when they fly." Still, it said that European authorities in Brussels, Belgium, would have the final say over whether to loosen rules across the continent. One academic said European regulators first followed the U.S. lead in banning the use of the devices during takeoff and landing and were likely to follow again now that the situation had changed. "American safety is regarded as a gold standard," said Joseph Lampel, a professor of strategy and innovation at London's City University and a critic of the current rules.