If the plan stays on schedule -- and there are plenty of skeptics inside and outside of FAA -- only three things will remain unchanged in the air traffic control system of 2010: controllers will give air traffic clearances and orders to pilots; pilots will fly planes; and planes can't fly through severe thunderstorms.

For the passenger, the plan, if executed properly, will mean better, faster, more frequent and safer service.

The need is great. After years of poorly executed FAA upgrade programs and a virtual ban on the building of new runways and airports because of community opposition, long delays and cancellations began rippling through the aviation system in the summer of 1999. The system is so saturated that one small problem can overwhelm the entire network. For example, a plane delayed five minutes on the runway at Newark International Airport now creates delays for more than 250 other planes as far away as Minneapolis, according to FAA documents. And individual planes are so full they cannot quickly accommodate spillover passengers from other flights that have been delayed or canceled.

Under a series of FAA-planned programs, the control of planes in the air and on the ground will gradually shift toward a satellite-based system. The FAA also plans to re-equip ground-based systems with digital radar and better software and controller displays. It also is counting on weather research that may someday give pilots and controllers up to six hours' notice to help them plan routes around bad weather even before it develops. The best meteorologists can do now is one hour.

Controllers and pilots also will have new tools. Controllers, for example, will be able to punch a few keys on a computer to determine whether an aircraft can take a direct route cross-country rather than follow jetways, sometimes called highways in the sky, in a zigzag pattern that allows controllers to better handle traffic, but adds minutes to flights and wastes millions of gallons of fuel every year.

Pilots will have moving video maps that will show nearby aircraft in the air and -- for the first time -- on the ground. This will not only be a significant new safety tool, but also will allow pilots to better follow orders from controllers.

Some FAA officials privately are nervous about showcasing the plan for fear of raising expectations too high. The plan is even bigger than the Advanced Automation System, which wasted $2 billion and sullied the FAA's reputation before it was canceled in 1994.

This time, FAA Administrator Jane Garvey is trying to avoid costly mistakes by avoiding huge, one-company contracts in favor of a gradual process she calls "build a little, test a little, deploy a little." She has converted some of the FAA's greatest critics, particularly the controllers' union, into cheerleaders.

"She's the one who said, 'No more grandiose schemes,' " said John Carr, president of the National Air Traffic Controllers Association, whose members not only received a huge raise last year but also are consulted in advance of any new equipment or procedures. "She's the real deal."

Unlike with the monolithic Advanced Automation System, which had a projected final cost of $5.4 billion, it is difficult to estimate the cost of a new system that is based on the sum of its more than 50 parts. The FAA estimates that it will spend at least $11.5 billion by 2010 on new facilities and equipment to enhance capacity. The full cost is certain to be more.

The plan is not intended to change the relationship between controllers and pilots, but should help them cooperate better.

For example, there will be less controller-pilot radio chatter, relieving pressure on both. Except for "safety-critical" orders such as turning to avoid other planes, most contact will be by "datalink" -- capable of a rapid-fire transmission of thousands of words a second to video screens in the cockpit. Current nationwide and local weather maps would be available in the cockpit instantaneously by datalink. Major airline companies already communicate with their pilots in this manner, but controllers do not.

The flying public already is seeing the results of some of the FAA's projects, although disgruntled passengers may not realize it. For instance, new equipment and building maintenance has cut sharply the number of incidents in which air traffic control center radar screens go blank, forcing controllers to use cell phones and backup systems to keep planes flying far enough apart.

Most controllers now work with color radar display screens that are fed by reliable computers that replaced old mainframes that filled large rooms. The days of vacuum tubes and green monochrome radar displays are all but over, and other display equipment is in development.

The new equipment that has been installed so far, however, mostly replaces aging and inefficient equipment that should have been junked years ago and does not fundamentally change the work done by pilots and controllers. "You've got modern infrastructure doing the old job," said an FAA contractor, who requested anonymity.

Now comes the real test: whether the FAA can develop a new generation of equipment that will allow the air traffic control system to handle much more traffic, while enhancing safety.

On Wednesday, the day after the FAA discusses its 10-year plan, Boeing Co. will announce its long-promised comprehensive satellite navigation plan. Federal sources said Boeing's plan will be mainly a set of principles with few technological details. One of the first questions already being raised is whether Boeing's plan and the FAA modernization program will be compatible.

Many aviation experts are skeptical about the FAA's ability to carry out the various plans, particularly given its track record.

Yet many FAA critics in Congress and elsewhere acknowledge that the agency is at least moving forward with a comprehensive plan. "They are doing better, but there are still high-profile failures," said a congressional staff member who has dealt with the FAA for many years.

The staff member and others say the FAA still suffers from slow decision-making and the inevitable conflicts of a "stovepipe" organization, in which responsibility for air traffic modernization is spread through many offices.

Jack Ryan, vice president for air traffic at the Air Transport Association, said he has often been frustrated with the FAA, but that ongoing flight delays and cancellations have helped the airlines and the FAA forge a better relationship. He pointed out that the FAA command center in Herndon now consults several times daily with the airlines to better plan the flow of traffic in adverse conditions such as thunderstorms.

"I can't believe that the FAA can be any more cooperative than they have been," Ryan said.

Meteorologist John McCarthy, who once spent years in a frustrating campaign to convince the FAA of the existence of a crash-causing violent downdraft called a microburst, took the unusual step last month at a symposium of praising the FAA publicly for its dedication to weather research.

However, McCarthy said in an interview that the process of putting that research into practice has been slower.

"On weather research, I'd give them an A," said McCarthy, who is now manager for scientific and technical program development at the Naval Research Laboratory in Monterrey, Calif. "That's a big change. But when it comes down to offering this to the customer, it's not going particularly well."

One of the most frequent continuing complaints is that the FAA still runs under a system in which one internal organization, or even an individual, can slow or block safety and capacity programs.

"There are still individuals in the FAA who can individually hold things up for months, and there are people in the FAA who don't want to change," said Ken Shapiro, marketing and communications manager for UPS Technologies.

The highest marks of all for the FAA come from its controllers union, which in the past had seemed to be constantly at war with the agency. Union president Carr said, "In the last five years, the change has been dramatic."