LOS ANGELES, Nov 24: Seven months before he crashed an airliner into the World Trade Center, Mohamed Atta was asking crop dusters in Florida an odd question about their planes: how far can they fly?

A Wall Street Journal report on Monday said the interest shown in crop dusting by the Sept. 11 hijackers and possible associates is one of the enduring mysteries of the recent terrorist attacks. Once discovered, it caused the first major post-Sept 11 scare and prompted authorities to ground crop dusters for five days.

Yet two months later, investigators still don’t know what these men were up to, despite thousands of interviews in the U.S. and Canada about their ventures into agricultural aviation.

Were terrorists planning to spread anthrax from a crop duster? That would be very difficult to do effectively, because anthrax droplets need to be small enough to float, and crop dusters are designed to spray droplets that don’t.

Perhaps they wanted to load a crop duster’s 800-gallon pesticide tank with another harmful agent, investigators speculate; or maybe they wanted to load a plane with explosive and crash it into something. Several strange inquiries, all along similar lines, have raised such concerns among authorities.

Mr Atta’s first known crop-dusting visit came in February. He and two other men who appeared to be of Middle Eastern origin drove to the municipal airport in Belle Glade, Fla., near Lake Okeechobee, and walked into South Florida Crop Care’s hanger.

James Lester, who cleans and loads crop dusters for the company, says Mr Atta pointedly quizzed him about how much fuel and chemicals the planes could hold, and became pushy when Mr Lester rebuffed his requests to sit in one of the planes. Finally, after mr Atta followed so closely behind that “he stepped on my heel,” Mr Lester told him he was too busy to talk anymore.

Atta and various men, apparently Middle Eastern, made repeated visits to the airfield throughout the spring and summer, employees there say. They usually stood off at a distance to watch crop dusters being loaded, taking off and landing, once videotaping them.

In March, Mr Atta and a man investigators suspect was Marwan al-Shehhi — the other hijacker-pilot who crashed into the World Trade Center — landed a small plane at an airport near tiny Copperhill, Tenn., by the Georgia border.

Danny Whitener, a pilot, says Mr Atta questioned him — again, in an aggressive manner — about a nearby chemical plant that he had just flown over, asking what chemicals were there. Informed that it was mostly empty, Mr Atta became angry and accused mr Whitener of lying, Mr Whitener says.

He also asked Mr Whitener about a nearby dam and two nearby electric power plants, both of them nuclear.

Later that month, Mr Atta went to the US Department of Agriculture’s Farm Credit Service office in Homestead, south of Miami, and inquired about borrowing money to buy a crop duster, people familiar with the matter say. He was told to check with the nearby Community Bank of Florida, which later received a call from someone who wanted to buy a crop duster — an unusual request, since few farms use crop dusters in the area.

Several weeks later, a man that South Florida Crop Care general manager J.D. “Will” Lee believes was Mr Atta returned to that airfield. This time, he wanted to know how far a crop duster could fly on a tank of gas, Mr Lee recalls.

“Nobody asks about the range of crop dusters — it doesn’t make any sense,” says Mr Lee, who related his account to the FBI.

A month later, Mr Atta and a companion returned by car, says John Rutkosky, then the airport’s manager. This time, Mr Atta asked mr Rutkosky about the range and fuel capacity of a British made Hawker jet and a Gulf stream turboprop parked there.

In Canada, a Middle Eastern man started showing up at crop- duster businesses in June, first visiting Farmair Ltd., in Regina, Saskatchewan, where he spoke to owner Norm Colhoun. He had an Arab-sounding name, but the men he encountered cannot remember it; they said he told them to call him Sam.

Mr Colhoun says the man asked for a pilot’s job, claiming to have flown crop dusters in Syria and Russian passenger jets.

Told there were no openings, he hung around for the day, observing and asking “funny questions” — including the planes’ range, says Mr Colhoun.

Later in June, the same man turned up 60 miles south at Arndt Air Ltd., a crop-dusting company in Weyburn. It didn’t have any pilot openings, either, but he showed up every day for a week, says maintenance director Dan McGonigle. Messrs. McGonigle and Mr Colhoun compared recollections, and both concluded they’d encountered the same man. The Royal Canadian Mounted Police are continuing to look for him.