NYPD probably couldn't take down a jetliner, key police source says

Instead, the city's air defenses are calibrated to take down a much more modest target.

"What was envisioned was a small aircraft ... coming down the Hudson," the source said.

"Al Qaeda was talking about targeting the West using crop dusters. There was a specific concern about using this type of aerial spraying of anthrax and some other biological chemicals. That also led to plans to equip our aircraft."

Police Commissioner Raymond Kelly, in a "60 Minutes" interview Sunday, answered in the affirmative when asked if the "NYPD has the means to take down an aircraft."

"I prefer not to get into the details, but obviously this would be in a very extreme situation," Kelly answered.

There was speculation he meant a jetliner, like the ones that took down the twin towers. The source suggested that's not the case.