American Airlines won F.A.A. approval last month for its pilots to use the iPad to read aeronautical charts. American received authorization last year to use the device instead of paper reference manuals. Executive Jet Management, a NetJets company owned by Berkshire Hathaway, received the F.A.A.’s permission in February for its pilots to read aeronautical charts on iPads.

Moreover, the F.A.A. said pilots at the two airlines would not have to shut off and store their iPads during taxiing, takeoff and landing because they had demonstrated that the devices would not impair the functioning of onboard electronics. Alaska Airlines pilots, like passengers, still have to put their iPads away during those critical phases of the flight.

“Each airline must submit a unique proposal on how they want to use the iPad and prove that both the device and software application are safe and effective for that proposed use,” said John W. McGraw, the F.A.A.’s deputy director of flight standards. Executive Jet Management, for example, had 55 pilots test the iPad on 10 types of aircraft to prove that it was reliable and that it would not interfere with flight instruments. The iPad was also subjected to rapid decompression at a simulated altitude of 51,000 feet.

Private and corporate pilots, however, do not have to go through the same approval process. According to F.A.A. regulations, they are responsible for determining what technologies are safe and appropriate for use in the cockpit. As a result, iPads are quickly becoming essential tools in planes ranging from Gulf Stream G650s to Piper Vagabonds.

“I don’t remember a time when one product seemed to get so much buzz and acceptance,” said Ian Twombly, spokesman for the Aircraft Owners and Pilots Association. “Many pilots approach new toys with skepticism, and the iPad seems to be almost universally appreciated as a cockpit device.”

There are now more than 250 aviation apps for the iPad, and one called ForeFlight is among the top grossing apps listed on iTunes. Its closest competitors are WingX, Jeppesen Mobile TC and Garmin My-Cast. Jeppesen is a subsidiary of Boeing, and Garmin is a leading manufacturer of global positioning and aviation electronic, or avionic, systems.