Travelers may soon pay more for a plane ticket because the Transportation Security Administration is raising the passenger security fee at U.S. airports.

Fliers currently pay $2.50 for each leg of a connecting flight, capped at $5 per one-way trip. Starting July 21, the fee will jump to a flat $5.60 per one-way trip. The $5 cap on one-way travel will disappear.

Congress approved the higher fees as part of the bipartisan budget act approved in December. The money will go to the general fund of the U.S. Treasury to be used to offset TSA costs for providing aviation security and to reduce the federal deficit.

The security fee has been built into airfares since the TSA was created after the Sept. 11 terror attacks.

Passengers buying plane tickets before July 21 won't have to pay the higher fees, no matter when they fly.

Separately, the TSA announced Sunday that travelers at more than a dozen airports in Europe, Africa, and the Middle East with direct flights to the United States will be asked to power up their electronic devices, including cellphones, during airport screening.

Devices that do not turn on will not be permitted on the aircraft.

Homeland Security Secretary Jeh Johnson told NBC's Meet the Press on July 6: "Our job is to try to anticipate the next attack, not simply react to the last one. We continually evaluate the world situation. And we know that there remains a terrorist threat to the United States. And aviation security is a large part of that."

Johnson added: "We in national security are very concerned about the foreign fighter flow going into Syria in particular from the United States, from European countries, other countries, and we're tracking that population. There are extremists within the borders of Syria. . . . We spend a lot of time talking to our foreign allies."

Based on the new electronics checks, the Department for Transport in the United Kingdom said passengers using British airports had been told that all electronic devices must be charged. The department declined to say which flights in and out of the United Kingdom would be subject to the new security checks, hoping the uncertainty would deter terrorists.

Certain passengers flying within the United States may also be asked to turn on their electronics at U.S. airports, said a person knowledgeable about the TSA plans. "It's only for a select number of people, who are already required, when they travel, to receive more extensive security screening," he said. "The focus is on international cities to the United States."

The move comes in response to intelligence reports that al-Qaeda members in Syria and Yemen may have developed bombs that can be hidden in mobile phones, with a view to bringing down U.S.-bound planes.

"It's important that the TSA stay ahead of terrorists who are planning new attacks," said Paul Hudson, executive director of FlyersRights, a passengers' rights organization.

Still, Hudson said the TSA provided "no real accounting" to justify the higher screening fee. Improved technology and expedited traveler programs, such as TSA precheck, "would presumably require less personnel and equipment," he said. "I think it's probably not justified to double the fee."