LOS ANGELES (AP) _ Planes intrude on controlled airspace at an alarming rate across the nation, a federal aviation official Thursday told a panel investigating the Aeromexico disaster that killed 82 people in August.

The testimony followed the city attorney's announcing he would prosecute pilots who violate airspace rules.

Federal Aviation Administration official Bill Hill testified that a task force instituted Sept. 15 found at least 175 airspace violations in a three- hour period one weekend nationwide.

''This is alarming,'' Hill told the National Transportation Safety Board hearing.

Hill, the FAA's assistant manager of special programs, said the number included only aircraft equipped with altitude encoders, which allowed them to show up on radar screens.

''I suspect the number of intruders would have increased if it included aircraft without altitude encoders,'' he said.

Before the hearing began, City Attorney James K. Hahn announced what he called the first airspace-intrusion probe by a criminal prosecutor in California.

He said the state Public Utilities Code makes careless and wreckless flying a misdemeanor carrying a maximum penalty of six months in jail and/or a $1,000 fine and license suspension for up to a year.

''That law will give us the authority to prosecute if the evidence warrants,'' Hahn said.

He said he will investigate whether Roland Furman, of Buena Park, flew his small Grumman plane into the Terminal Control Area, or TCA, over Los Angeles before the Aeromexico DC-9 collided with a different private plane Aug. 31, killing 67 people in the planes and 15 people on the ground.

Investigators have said the plane that collided with the DC-9 also violated the TCA.

A TCA is controlled airspace, usually 25 to 30 miles around an air traffic control facility, where all aircraft are subject to operating rules and pilot and equipment requirements.

Furman's plane popped up on an airport flight controller's radar screen while the controller was dealing with the Aeromexico jet. This was before the jet collided with the other small plane, which the controller says did not appear on his screen.

Hill told the NTSB hearing testified that the FAA task force concluded its study of all 23 TCAs nationwide on Oct. 15 and submitted more than 40 recommendations to the FAA administrator.

One recommendation that was immediately implemented, he said, increased the penalty for violating TCA airspace so that a pilot now must pass a written test after being suspended in order to regain his license, and no suspension can last less than 60 days.

Other recommendations awaiting action include simplifying TCA design, a ban on student pilots within TCA airspace and a requirement that all planes flying within a TCA be equipped with transponders that show altitude as well as location, he said.

John Norris, accident prevention coordinator for the FAA in Los Angeles, testified that in the months before the Cerritos crash, hundreds of private pilots attended seminars where the theme of collision avoidance had been given special emphasis.

''Collision avoidance is 'See and be seen,''' he said. ''It's ironic that after this maximum effort,'' the Cerritos crash occurred.