"It's a dangerous circumstance that we just need to address," said Dean Headley, co-author of the closely watched Airline Quality Rating, an annual survey of aviation performance by Wichita State University and Saint Louis University.

Gregor acknowledged that "we currently do have a higher percentage of developmentals in our facilities than we have had in recent years," but he said the agency's training programs "are set up to maximize quality training, both in the classroom and on the job."

Addressing the PATCO Effect More than 8,700 air traffic controllers were hired after President Ronald Reagan fired 11,000 striking members of the Professional Air Traffic Controllers Association in 1981.

In what's commonly called the PATCO Effect, the first big wave of post-PATCO controllers began hitting the retirement age of 56 in fiscal year 2007. More than 820 controllers retired, 29 percent more than the agency had projected.

The FAA's controller workforce plan says nearly 5,000 more will be eligible to retire in the next two years.

As the experienced workers have departed, the FAA has gone on a hiring spree, with an eye toward taking on about 15,000 new controllers by 2017.

The FAA hired 2,196 controllers in fiscal 2008, its records show. Only 720 had previous experience in the military or at other FAA facilities. The rest, 67.3 percent, were developmental controllers.