LOS ANGELES — Concerns about the Air Force’s problem-plagued fleet of F-22 Raptor fighter jets led Defense Secretary Leon E. Panetta to restrict flights of the aircraft because of problems with its oxygen systems that can cause its pilots to become disoriented mid-flight.

In addition, Panetta wants a monthly progress report on the investigation into the root cause of the F-22’s oxygen problems and ordered the Air Force to speed up the installation of an automatic backup oxygen system.

Panetta also called on Navy and NASA personnel to find a solution.

The announcement is the latest blemish for the controversial F-22, the world’s most expensive fighter jet, which was made by Lockheed Martin Corp. and has never been used in combat since entering service in 2005.

Since 2008, F-22 pilots have reported more than a dozen incidents in which the jet’s systems weren’t feeding them enough oxygen, causing hypoxia-like symptoms in the air. Hypoxia is a condition that can bring on nausea, headaches, fatigue or blackouts.

The malfunction is suspected of contributing to at least one fatal accident and led to the grounding of the entire F-22 fleet last year for nearly five months. The Air Force acknowledged two weeks ago that some pilots are refusing to fly the F-22 at the risk of significant reprimand or even discharge from the Air Force.