JetBlue and Delta were the first two airlines to let customers use electronic devices during takeoff and landing, and now United Airlines is joining the pack. The company announced today that it was providing electronics-friendly cabins for domestic flights, allowing passengers to use their phones, tablets, and other devices throughout the entire duration of a flight — provided theyre in airplane mode, of course. The shift comes after the Federal Aviation Administration officially allowed the use of electronic devices through all phases of flight, addressing a long-standing consumer complaint. For the moment, only Uniteds mainline flights are included, but the company says it is working with its regional partners to bring the same opportunities to passengers on United Express flights by the end of 2013.