Jetliners landing at the Washington region’s three airports will save both fuel and emissions by descending smoothly to the runway, the FAA says. (Ricky Carioti/The Washington Post)

Friends or family flying in to spend the holiday weekend in the Washington region? Ask them if they noticed the glide when their plane began to descend from cruising altitude.

Chances are the answer is no, but the Federal Aviation Administration is touting the 2.5 million gallons of fuel that jetliners landing at the region’s three airports will save each year, and the 25,000 fewer metric tons of carbon emissions, now that they can glide down to the runway.

The improvements came to Baltimore-Washington International Marshall Airport this month and already were in place at Reagan National and Dulles International airports. Fuel and emissions are saved because planes can descend smoothly — think of a straight line — from cruising altitude instead of the step-by-step process — think of a set of stairs — that they’ve been using for decades.

The glide process is one part of the FAA’s NextGen system , a revolutionary $40 billion overhaul of the way traffic is managed in the increasingly crowded skies. As NextGen rolls out in the next decade, it is projected to save time, fuel and emissions by allowing more direct routes, more efficient use of airspace as planes get to and from altitude and better management of planes awaiting takeoff.

“The whole point of NextGen is to get air travelers to their destinations safely and on time,” said FAA Administrator Michael Huerta, “and this is never more important than during the busy holiday season.”

The aviation agency is still smarting over criticism at a House Transportation Committee hearing last week. Committee members said the NextGen program was “stalled” and “broken,” and one member raised doubt that the FAA would meet critical deadlines.

Not invited to the hearing, the FAA responded the following day by announcing that some parts of the NextGen system were in use at the two busy airports in Dallas. The agency followed the event in Dallas with a news release Sunday pointing to the NextGen elements in use at the three Washington-area airports, describing them as “three state-of-the-art, satellite-based highways in the sky running side by side” to take planes to the three airports.

The House committee did hear last week from Calvin Scovel III, inspector general of the Transportation Department, who has been critical of NextGen’s progress.

An inspector general’s report in September said one of the centerpieces of the NextGen system was “years away” from implementation. The system, called ADS-B, couples GPS technology and other satellite-based systems with 634 FAA ground radio stations. ADS-B is a critical element that will replace a radar-directed system developed during World War II with a faster and more accurate means to manage air traffic.

While the FAA has created the ground stations, the inspector general’s report said it hadn’t modernized other systems to make it useful.

Airlines, which must make multibillion-dollar investments in NextGen, have been reluctant to install the equipment until they are confident that the FAA is close enough to implementation to make their investment worthwhile.

The FAA met privately with airlines and other stakeholders last month to hear their concerns. A second meeting with the group has been promised.