The NYPD (search) is beefing up anti-terror efforts at concert halls, sports arenas, theaters and other places where large crowds gather as the city turns a deeper shade of orange than the rest of the nation, law-enforcement sources say.

The intercepted "chatter" that on Sunday spurred the feds to hike the national terror alert (search) to high-risk orange indicated not only that terrorists might use airplanes as weapons, but that they want to target large groups of people, the sources said.

They did not identify which New York sites would get the added protection, but said they would be places like Lincoln Center (search), Madison Square Garden (search) and Radio City Music Hall (search).

Other sources said that while the chatter pointed to New York, Washington and Los Angeles as potential targets, terror talk also has named specific high-profile objectives elsewhere in the United States.

The sources declined to say where.

But the White House remains a prime target because Al Qaeda likes to try again where it has failed, a source said.

Some of the new intelligence comes from an Al Qaeda insider captured recently in Saudi Arabia, sources told The Post.

That operative's story matched some information from Turkish terrorists captured after the Nov. 15 bombings in Istanbul, said the sources.

The Turks also offered "vague outlines" of a spectacular terror act on U.S. soil before year's end, the sources said.

Underscoring the possibility of another airliner attack are intelligence reports that Al Qaeda operatives may have gotten jobs as commercial airline pilots in countries where security is lax, NBC News reported last night.

Because of the threats, Air Force fighter jets will constantly patrol New York, Washington and Los Angeles, said The Post's sources. Random patrols are planned over other cities, and anti-aircraft batteries are being deployed around Washington.

The Big Apple, which has been at level orange since Sept. 11, is making extra preparations for the new threats.

At a press briefing with Mayor Bloomberg and Gov. Pataki, Police Commissioner Ray Kelly agreed when a reporter called New York City's alert level "Orange Plus."

"There's a series of things that we're doing - kind of under the rubric of our Orange Alert - that are increases, you might say, from what we've done in the past few months," Kelly said.

There will be more cops on the transit system and other locations, including Midtown, the Financial District and area airports.

Commuters can expect more checkpoints at bridges, tunnels and some street locations.

Among the cops being deployed are the highly visible and heavily armed "Hercules" teams, whose very presence may scare off terrorists, and less-conspicuous but equally eagle-eyed forces, Bloomberg said.

Additional reporting by Stephanie Gaskell and Vince Morris