"We must do all that we can to ensure that the skies over California are safe," Feinstein said. "Unfortunately, we are losing large numbers of air traffic controllers to retirement, and I'm very concerned that the Federal Aviation Administration is falling behind on filling these vacancies with properly trained and certified replacements."
The Inspector General's Office of the U.S. Department of Transportation will examine traffic controllers at LAX and at the Terminal Radar Approach Control centers or "TRACONS" in San Diego and Sacramento, which direct traffic between airports.
FAA officials have acknowledged that control towers have suffered from a recent surge in retirements by able and experienced workers.
"We've known that we will lose most of our experienced air traffic controllers in the decades ahead, and we've been preparing for it," said FAA spokesman Ian Gregor.
The agency projects that more than half of its roughly 14,800 air traffic controllers are expected to retire by 2017.
Gregor said more than 1,800 controllers were hired last year, and plans were to bring on the same number again this year.
The FAA recently began offering bonuses of as much as $25,000 to retirement-eligible controllers willing to keep working.
The agency's guidelines call for LAX to have between 39 to 47 controllers on its staff. The airport currently has 43, though four are trainees with no previous FAA experience.
Trainees do count toward the authorized total under FAA rules, a fact that concerned Feinstein's office and would be a subject of the investigation.
Officials with the National Air Traffic Controllers Association welcomed the audit.
"This is extremely important," said Mike Foote, local representative of the association and a controller at LAX. "We feel that the FAA has been playing fast and loose with the facts. If we aren't understaffed at LAX, why do we have three to five people working overtime every day? Even then, we still run short."