SAN DIEGO -- Sen. Dianne Feinstein, D-Calif., sent a letter to President-elect Barack Obama's nominee for transportation secretary warning about a chronic shortage of air traffic controllers at a San Diego radar facility and at Los Angeles International Airport.

In the letter to Ray LaHood, Feinstein called on the Federal Aviation Administration to take immediate steps to boost staffing levels and retain veteran controllers at LAX and at the Southern California Terminal Radar Approach Control, or TRACON, facility near Miramar.

According to the senator, the number of fully certified controllers at the Southern California TRACON facility dropped from 236 in 2004 to 164 in April 2008.

"I believe that the current staffing situation represents a serious accident waiting to happen," Feinstein wrote.

Feinstein cited an "ongoing runway incursion problem that has been attributed in part to controller fatigue" at LAX, which is home to the fourth-busiest air traffic control tower in the nation.

She also said "operation errors" at TRACON, which handles more flights than any other similar facility in the world, are way up.

In November, a controller mistake put a Southwest Airlines jet and an Alaska Airlines jet on a collision course while both planes were maneuvering to land in San Diego, according to Feinstein.

"Thankfully, onboard collision warning devices have warned pilots to take evasive action, and disaster has been averted," Feinstein wrote. "But these incidents remind us that the Southern California airspace demands the most experienced, most savvy controllers in the nation. I am not confident that the FAA's current approach to staffing will meet these ongoing demands."

Feinstein said the "massive staff turnover" is straining the air traffic control system in Southern California.

She recommended the FAA consider offering incentives to keep experienced controllers on the job, expand incentives to attract certified controllers from other regions and alter the training system to handle a massive influx of new controllers as quickly as possible.

At Feinstein's urging, the Department of Transportation's inspector general has opened an investigation into the problem.