The plane has traveled all the way from Delaware to move in slow circles over Lodi. It hasn't exactly blended in.

The city is small enough that when a medical helicopter makes one pass overhead, citizens look up. When gang problems flare and local police officers team up with the California Highway Patrol to make use of a helicopter, police dispatchers are besieged with calls from citizens.

So, when white planes began circling over Lodi about four weeks ago -- around the same time scores of FBI agents converged on the city to conduct a terrorism investigation -- people took notice.

"He's doing something. He's doing some reconnaissance," said Lodi resident and pilot Arlene Farley, who even got out binoculars to peer up at one of the planes.

What the planes are doing remains a mystery, though most people believe the activity coincides with the FBI investigation that led to the arrests of five Lodi men. In other parts of the country, small planes have flown in circles over cities also under investigation on ties to domestic and international terrorism.

How long will the planes stay in Lodi?

What are they doing?

Where are they from?

Can they really see anything from that high up in the sky?

Assuming they're government-run, how much are they costing taxpayers?

Some of those questions go unanswered as local and federal officials remain mum.

At least one question, however, is partially answered -- though that leads only to more mysteries.

One of the planes circling over Lodi is registered to a Delaware company. Northwest Aircraft Leasing Corp. is based in Newark, Del., according to Federal Aviation Authority records.

The company lists an address, but it only leads to a box inside a mailing store, located in a town with a population of a little more than 28,000.

Northwest Leasing isn't listed on the Better Business Bureau's Web site, but it does reveal that several other businesses, including online weight loss programs, share the same address. One says it has a "Dept. 357," another simply uses the numeral sign. An appliance sales company lists "PMB 319," otherwise known as a mailbox.

Employees at a dime store down the street and with the city's building department both said the East Main Street building isn't big enough to have "suites."

Newark isn't a large town, and the state of Delaware isn't that big, either. However, doing business in the state is easy: Incorporating a business only starts at $89, and annual franchise taxes can be as low as $60, according to Web sites offering to help potential business owners get started.

"When companies lease their aircraft out of Delaware, it's because they don't have to pay taxes out of Delaware," said Ross Dubarry, operations manager for Hayward Executive Airport.

Officials remain silent

A Lodi businessman and public figure, who didn't want his name used because he thought people would think he was crazy, said he called the Federal Aviation Authority to ask about the planes and was told that the pilots were likely listening to cell phone conversations and using infrared to track people. He was also told the planes were flying out of the Hayward airport.

When given the tail number of the Delaware-owned plane, Dubarry -- who is new to the area and didn't know where Lodi was -- initially said it sounded familiar and that the plane was being housed at the airport. After consulting a computer for several minutes, though, he told a reporter that there was no record of the plane.

Area airports had no record of the plane, either.

Local and federal law enforcement officials also aren't saying much.

FBI spokeswoman Angel Armstrong wouldn't comment on the cell phone and infrared tracking information that the local businessman heard about from the FAA.

"It sounds like that's a bunch of people throwing around some speculation, and that would be considered part of an ongoing investigation that we're not going to comment on very much at all," she said.

When asked about the planes earlier this month, Keith Slotter, former FBI special agent in charge in Sacramento merely said that the agency has a number of investigative tools.

"It's obviously surveillance of some sort," said Lodi resident Kay Duelfer, who has been watching the planes. "It would just be nice if they would say, 'OK, we're here, this is what we're doing.'"

Local officials aren't talking, either.

"I can't tell you much about them; they're not mine," said Lodi Police Chief Jerry Adams, who also hears the planes circling overhead when he is home.

When first asked about the planes earlier this month, Adams had no knowledge of them. Now, he simply won't comment further.

When police officers heard that the planes flying over Lodi were tied to an unknown corporation in Delaware, they weren't surprised.

They joked that the planes overhead are watching their every move, and that if a reporter dug far enough, she'd just vanish one day. They also didn't want their names published.

It's not likely that the planes will suddenly do away with local journalists, but when reporters for the New York Times began investigating planes operated by private corporations with no real addresses, their search ultimately led to the CIA.

According to a May article of more than 2,500 words, citizens had agreed to let government officials list shells corporations in their name, and the businesses then operated aircraft. The planes were coincidentally flown to places around the world when suspected terrorists happened to be moved.

Are the Cessna 182s flying over Lodi getting ready to whisk people away to a far-off place, or perhaps Guantanamo Bay, Cuba? That's probably not likely for now, since the five men arrested in Lodi have not been charged with terrorism.

Two men are charged with lying the FBI agents about their participation or knowledge of terrorist training camps in Pakistan. Three other men are held solely on immigration violations.

In the meantime, FBI agents continue to swarm Lodi, and the planes continue to circle.

Surveillance ideas

For the most part, the planes are flying in continuous circles to the left, which could indicate that they're equipped with forward-looking infrared, known as FLIR.

According to a March 2003 publication of Fields of View -- put out by FLIR Systems, which sells the surveillance equipment -- FLIR can be used in fixed wing planes just like the ones flying over Lodi. Using it, a plane flies in left-hand circles over the area under surveillance, using thermal imaging to track people.

The publication recommends using a Cessna 182 -- the same type of plane flying over Lodi.

Could that be what the planes are doing up there? Perhaps.

In the last few years, circling planes seem to have accompanied federal terrorism investigations. Portland, Ore., and Bloomington, Ind., were among two cities where citizens called police and local media.

In Lackawanna, N.Y., where six men were detained in a similar terrorism investigation in September 2002, Cessna planes were used to track e-mails, cell phones and wireless Internet activity, as well as keeping track of some suspects, Police Chief Dennis O'Hara said.

"One day a plane was just circling and just circling, and I knew it wasn't the traffic plane because I knew its schedule," he recalled.

If that's the case in Lodi, Adams isn't saying and patrol officers don't know.

Lt. Bill Barry said he talked to dispatchers in case residents called.

"We've told the dispatchers that if people call in, as long as (the planes) stay above 1,000 feet they're not breaking the law," Barry said.

Large airliners that fly above 18,000 feet must file flight plans and notify the FAA of their purpose. But smaller aircraft are only an "unidentified blip" on a radar screen, said Mike Fergus, a Seattle-based FAA spokesman.

As long as the small planes follow "visual flight rules," referred to as VFR in flight lingo, it's no concern to the FAA. It's not much different, he said, than when the average citizen uses a vehicle to go to the grocery store: Federal officials don't have to be notified.

The planes aren't as loud as they could be. After all, helicopters flying overhead are much closer and much louder.

Duelfer doesn't live far from Lodi Memorial Hospital, so she often knows when a medical helicopter is picking up a patient and heading for a larger hospital or a trauma center.

She's been around planes for most of her life: Her father was a pilot, her uncle was a captain in the military and her husband flew planes at Travis Air Force Base.

When she began hearing planes over Lodi, she looked up. Weeks later, she's still looking up.

"I'm just nosy enough that I want to know what they're doing," she said. "I have this mental picture of them up there with their night goggles saying, 'Oh, there's that woman who watches us every evening for 20 minutes and has a couple smokes with her dog nearby.'"