ALTON, N.H. (AP) _ After fumes knocked out her pilot son, a 71-year-old woman, also a pilot, took the controls of a small plane and tried to land before she was also overcome. The plane cruised over three states before it crashed, killing both.

The two-hour drama began in Connecticut Friday morning and continued in the skies over Massachusetts and New Hampshire. Air traffic controllers coached the increasingly groggy passenger, and a private pilot spotted the plane, established radio contract and tried to give her instructions.

Authorities said they suspected carbon monoxide poisoning caused the accident.

David Riach, 46, of Babylon, N.Y., was the owner and pilot. Police said his passenger was Dorothy Riach, 71, of Morris Township, N.J. They were heading from Farmingdale, N.Y., to Saranac Lake, N.Y.

Air traffic controllers heard the woman panic, then radio for help.

``David, David, David! Wake up!'' the voice of a frightened woman was heard by air traffic controllers in Westbury, N.Y., The New York Times reported today. Air traffic controllers at Sikorsky Airport in Stratford, Conn., and the pilot of a private plane also heard the woman's distress call.

A National Guard helicopter was sent out to try and talk her down, but it couldn't catch the plane, which officials said may have been on autopilot.

Private pilot Harold Hamre saw the plane and pulled beside her, trying to coach her through a landing at Sikorsky. But he and ground controllers lost radio contact as Mrs. Riach became groggy.

``She talked to us quite a long time,'' Hamre told the Concord Monitor. ``It looked really good for a while and everybody felt good. Then she started complaining about being tired.''

Michael O'Donnell, an official at Sikorsky Airport, said the woman became lethargic, apparently affected by the same fumes that overcame her son.

Mrs. Riach reported having some flight experience, but said she did not know how to fly the Piper, Hamre said. He followed the plane to New Hampshire, where he witnessed the crash.

``It's kind of sad,'' he said. ``We weren't able to help her come down to a safe landing.''

Alton Police Sgt. Tracy Shattuck said both mother and son were licensed pilots.

The blue and white single-engine plane clipped the treetops and crashed near Lake Winnipesaukee in central New Hampshire. Rescuers searching through the dense woods found the seats and bodies thrown from the plane.

``There was no doubt there were no survivors,'' said Jerry DeLemus, one of the first to reach the wreckage.

Neighbors told the Monitor that Riach was an experienced pilot who worked as a computer programmer for Citibank. He and his mother were headed to his cabin in upstate New York for the weekend.

No one answered the telephone at Riach's home or his mother's house, and messages were not returned. Police in Morris Township said they had been asked to contact the Mrs. Riach's family, but had been unable to do so Friday.