The way we prevent planes from crashing into one another hasn’t changed much since World War II. But by 2020, and in some places much sooner, air traffic control, navigation, and the nature of flight itself will undergo a transformation as momentous as the invention of radar itself. The results, according to the Federal Aviation Administration, will be safer skies, fewer delays, and significantly lower costs – for the taxpayer, at least.

To understand just how different Next Generation technology, or NextGen, is from our current air traffic control system, it helps to know a little about the one we have now. The first thing to know is that pilots generally have little idea where other planes are. All of that knowledge resides with the air traffic controller, and even his or her picture of the sky is limited. Ground radar over major air routes only sweeps the sky once every 12 seconds, while radar at terminals sweeps every four. In four seconds, a jet can travel several miles.

Over oceans and certain flight routes without radar — say the interior of Australia and across Greenland, planes have historically been more or less invisible to controllers and each other. Pilots have a limited ability to adapt to changing conditions, can become trapped at certain altitudes by the possibility that other planes are above them, and must put large distances between themselves and other planes to account for the overall sluggishness of the system.

A digital mesh network

If the existing air traffic control system is operated more or less like a giant ham radio club, then NextGen is the dawning of the Internet age. Planes in the sky are part of a digital mesh network, in which every one of them can see and be seen by all the other nearby planes. They can communicate with one another without interfacing with the ground, transmitting their heading and velocity as well as a host of other information — weather, conditions, even the margin of error of their own instruments.

All this data is transmitted once per second and allows pilots to react to one another in real time, fly in tighter formations, stick with pre-programmed computer-plotted routes through crowded airspace and save fuel by shifting engines to idle when descending into airports.

Despite these benefits, many airlines have made it clear they’re not going to implement the most important portions of NextGen until the FAA forces them to. The CEOs of both Delta and US Airways argue that air traffic isn’t growing fast enough to justify the increased density of planes in the sky that is one of the primary benefits of NextGen. It doesn’t help that while NextGen means the FAA’s costs will go down, the cost to the airlines of the transition will be on the order of $25 billion.

Standards finalized

The intransigence of air carriers aside, the most important technical standards for NextGen have been finalized. Much of the equipment has been put through its paces, and in some parts of the world, including the U.S., some of its most important components are already in service. By the end of 2012, the U.S. will be fully covered with the radio receivers that will replace conventional radar, according to R. John Hansman, director of the International Center for Air Transportation at MIT.

NextGen is satellite enabled, which means that airplanes in the system can use GPS to determine their location. But this doesn’t mean the system is dependent on GPS, says Hansman, who points out that airplanes have long had other sources of location information, including inertial navigation, which uses dead reckoning to determine location based on last known position, as well as transponder-based radio navigation systems. The FAA will also continue to maintain some radar installations, which will also be a last line of defense against “uncooperative targets, in other words, terrorists,” says Hansman.

Some carriers are already enjoying some of the benefits of the core communication system of NextGen, known as Automatic Dependent Surveillance-Broadcast, or ADS-B. By 2015, most of the countries in Europe and Asia will require that all planes in their airspace be equipped with ADS-B “out,” which broadcasts the location of a plane. The same technology will be mandated in U.S. airspace by 2020.

UPS has been experimenting with ADS-B since 1996, according to Mike Mangeot, a company spokesman. Its entire fleet is equipped with both ADS-B in and out, which means its planes not only broadcast their location but can see the location of every other plane with the equipment. UPS has a special incentive to pioneer this technology — at its packed world-wide air hub in Louisville, delays of even a few minutes can be problematic. ADS-B also allows UPS to engage in “Continuous Descent Approaches,” in which “an aircraft coasts into an airport with its engines at idle thrust, rather than stepping down in a traditional landing. This reduces noise and nitrous oxide emissions and reduces fuel consumption,” says Mangeot.

But who will pay?

The fact that NextGen will reduce costs for the FAA, by eliminating the need for many expensive radar installations and the overtaxed air traffic controllers who run them, has led some in industry to conclude that the agency should foot most of the bill.

The FAA has already spent $4.4 billion of the $7 billion it currently has allotted to realize NextGen. To incentivize airlines to cover the cost of retrofitting their own planes with ADS-B and, in some cases, new navigational systems, which Hansman says can run to hundreds of thousands of dollars a plane for a large commercial aircraft, the agency is considering giving carriers who install the equipment before the 2020 deadline privileged access to airports.

If that doesn’t work, there’s always the argument that, as fuel costs rise, the routes that can be plotted with precise satellite navigation will save enough fuel to justify the cost of retrofits. Southwest Airlines has already made this kind of commitment, and is saving $16 million a year in fuel as a result. It’s also been proposed that the FAA subsidize airlines’ costs for upgrading, but that seems unlikely in the current fiscal climate in Washington.

Many of the benefits of NextGen, such as safety and improved awareness for America’s many small airplanes, are public goods that are not likely to be justified on the grounds of cost alone, anyway. That’s just one of the reasons it has taken this long to realize a system that was first proposed in the 1980s. Another is that a misconception remains that NextGen is a monolithic enterprise that will be realized all at once, and can’t be rolled out in pieces.

“NextGen is completely based on an incremental rollout; it’s designed to be scalable” says Laura Brown, deputy assistant administrator for public affairs at the FAA. One of the dimensions of the technology that will continue to scale is a feature of NextGen that will be present only in the U.S.: A high-bandwidth data channel, known as UAT, which will allow ground controllers to send almost any kind of digital communication to planes. Literally, an Internet in the sky.

Top Image: The interior of a Douglas DC-2, which was introduced in 1934. Photo/Courtesy FAA

Christopher Mims is a contributor to Good, Technology Review and The Huffington Post, and is a former editor at Scientific American and Grist.org. His last article for Txchnologist considered the possibility that the U.S. could become a net exporter of liquefied natural gas. He tweets @mims.