From Monday through Friday, Frank Hatfield oversees 3,100 air traffic controllers who direct thousands of flights over an area stretching from New York to Virginia. Working out of offices near John F. Kennedy International Airport, he supervises the Federal Aviation Administration's operations that prevent planes from crashing into each other or veering into bad weather.

But on weekends, Hatfield, 51, often joins members of the New York Ghost Chapter -- a group that searches houses, graveyards and businesses, such as New York's Capitol building in Albany, for signs these sites are haunted.

Hatfield describes it as just another weekend hobby, and his boss, Arlene B. Feldman, FAA regional administrator for the eastern region, said she has no problem with his unusual interest. Even bureaucrats "need to have an outlet," she said.

Hatfield sees some similarities between ghostbusting and his day job, where he has responsibility for air safety and the FAA eastern region's $400 million annual budget.

Both, he explains, are driven by his love of science.

The attraction of ghost chasing, he says, is the desire to find scientific answers to unexplainable phenomena, such as the 60-pound iron doorstop he saw move across a level floor and the tug on his pants he felt when he was alone in a supposedly haunted house.

"It's an opportunity to gather and study data," Hatfield explained. In ghostbusting, "you look for the illogical things, the kind of things that don't make sense." He said he has been interested in the supernatural world since his youth. But it was not until his wife told him to get a hobby that he took up ghostbusting.

"With the day job, you have to take care of all the airplanes and people and make sure you have the best service you possibly can. That's demanding in its own right, and it's exciting because it's always a challenge," he said. "This is a different kind of excitement -- a whole different kind."

Although he spends much of his free time searching for ghosts, he doesn't believe in them -- yet. The scientist in him wants proof; he wants to see a ghost for himself. Until then, he remains what he calls "an open-minded skeptic."

In many ways, Hatfield is a walking contradiction. He's an aviation expert who prefers to drive (so that he is always reachable by pager or cell phone). His demeanor is often playful; he refers to everyone as "pal" and "friend," but he quickly switches to the quiet efficiency of a police captain when talking to air traffic controllers. He loves no-nonsense hard facts that can be charted but keeps a life-size ceramic figure of the Blues Brothers in his office, joking that he, like the duo, is "on a mission from God."

Thus, it may be logical that Hatfield would turn to technology and science to try to understand the spirit world.

For a ghostbusting assignment in Beekman, N.Y., earlier this year, Hatfield, his wife, Pat, and others in his group went equipped with digital cameras, tape recorders and flashlights. The group doesn't charge for its investigations but asks that expenses be covered if they have to travel outside New York.

Ghostbusting is usually done at night because that's when ghosts are most active, said Fran Bennett, a parapsychologist who founded the New York Ghost Chapter and is a true believer. (Bennett called "Poltergeist" the most inaccurate portrayal of the spirit world and Nicole Kidman's film "The Others" the most realistic.)

The potentially haunted structure in Beekman, 66 miles north of New York City, is a recently refurbished 18th-century hotel, with a general store attached to the side of the house. It has hidden passageways and false walls in the basement, where the former owners hid liquor during Prohibition.

The current owners, Paul and Amy Hyatt, bought the building a year ago, moved into the hotel and began selling antiques out of the general store. Soon afterward, the couple and their two sons began hearing voices and seeing objects fall off shelves. Occasionally, said Amy Hyatt, she had difficulty breathing. At other times, the temperature in the house dropped suddenly.

Paul Hyatt said new compact discs, especially by Johnny Cash or Elvis Presley, would skip or cut off. "They don't like Johnny Cash," he said.

Hatfield asked the couple his usual series of questions.

Did anyone die in the house? (Answer: No, but they used to lay out dead bodies in the parlor, where family and friends could view them.) Do they think the ghost is male or female? Old or young? (The owners thought it was a boy because the ghost would play with their 5-year-old son.)

While questioning the property owners, Hatfield looked for signs of alcohol or drug abuse but saw none. He also tried to figure out if the Hyatts would have anything to gain by getting him to declare their place spooked. They said they had no plans to market the haunting. (But more on that later.)

Next, Hatfield walked through the general store and placed digital tape recorders in several locations to capture any voices or sounds. Then, in a slow, relaxed cadence, he introduced himself to any ghosts that might be hanging around: "Hi, guys, I'm Frank. I have a bunch of people here with me. Nobody means you any harm. We're friendly, and I understand you're friendly. We're just trying to document the fact that you're here."

He continued: "If you could let us know you're here, maybe by reaching out and maybe touching one of us that's in the room right now. Anytime you want to make yourself known, make a sound. We can record your voice with this recorder. If there's something you want to say, it's on the table by the front door." Then he and the others left the room.

"Ghosts like to interact," he explained later. "I'll say, 'I hear you like to touch people. Well, let's get it on.' "

The group split up. Hatfield explored the basement, shining his flashlight in dark spaces, searching for signs of paranormal activity, such as voices or objects moving unexpectedly. Armed with a flashlight, he walked carefully. The basement was cool and damp, with limestone walls and floors. After 20 minutes, his group emerged, covered with cobwebs.

Meanwhile, Bennett had set up several digital video cameras and motion detectors on the second floor. Everyone was told to leave the area. An hour later, a motion detector sounded an alarm, and everyone raced upstairs.

One videotape showed several large balls of light shooting from one room through the hallway to another. Bennett said those were orbs or spirits.

Amy Hyatt's eyes got teary as she heard Bennett's explanation. "I knew there was something. I'm just glad to have proof -- proof that there is something here," she said.

Hatfield smiled and gathered his equipment. He later said he remained unconvinced. "Maybe it was mice. You don't know. It's an old house," he said.

The balls of light did not scare the Hyatts out. On the contrary, the general store now sells tarot cards and other items related to the paranormal. And the second floor is rented by someone who likes the idea that the room is haunted, Paul Hyatt said.

Hatfield, though, remains ever the scientist. "The jury is still out," he said. "If I say 'Yes, I believe,' then I close off my ability to be objective."

Ghostbusters Clint Tibbs, left , and Frank Hatfield inspect the cellar of the Beekman Hotel, 66 miles north of New York City.Unexplained phenomena at the Beekman Hotel, such as strange noises and objects falling off shelves, are being investigated by the New York Ghost Chapter.Pat Hatfield extends an arm to feel temperature changes in an antique room at the Beekman.John Alfano and Fran Bennett wield metal rods and electromagnetic-field meters near what may be unmarked graves in Beekman, N.Y. Bennett is president of the New York Ghost Chapter, whose members spend their free time investigating the paranormal.