HILO, Hawai'i — About 15 Coast Guard, county and private aircraft scoured the Big Island for a second day yesterday, searching for a missing Cessna tour plane with an experienced pilot and two Japanese on board.

Yesterday's search covered more than 2,500 square miles, or an area roughly four times the size of O'ahu, before being suspended about 8:30 last night.

Rescue air crews with the U.S. Coast Guard aboard two H-65 Dolphin helicopters and two C-130 search planes were to resume the search at first light today.

"We are exhausting the search area with as many resources as we can bring to bear," said Lt. Cmdr. Kevin Floyd, supervisor of the Fourteenth Coast Guard District Command Center in Honolulu.

The single-engine Cessna 172 operated by Island Hoppers left Kona airport on a three-hour tour around the Big Island on Tuesday morning at about 10:15 and was last seen at 12:45 p.m. the same day in the Kilauea area.

The missing pilot was identified as 40-year-old Katsuhiro Takahashi, an experienced pilot and flight instructor, who fellow pilots said was well equipped to handle any emergency in the air.

Rescue workers turned up two potential leads nearly 100 miles apart sides of the Big Island in the search for the missing plane yesterday.

A fisherman reported seeing debris about a mile off the Big Island coast northwest of South Point about 8:30 a.m. yesterday, but a Coast Guard aerial search of a 10 square-mile ocean area turned up nothing, said Big Island Deputy Fire Chief Glen Honda.

Also yesterday, a U.S. Coast Guard C-130 search plane flying above the Pi'ihonua area detected a brief radio signal that could have been from the missing plane, but the transmission was too brief to allow crews to get a fix on the source, fire officials said.

A ground team searched the Mana Road area near Hakalau near the center of the Big Island, but was called back after finding nothing, Honda said.

Honda had said the radio transmission was imprecise. "This signal where they picked it up could have been bouncing off of something else, and that's why they picked it up in that area. It doesn't necessarily designate that that's where the locating device is."

All commercial and tour flights and nearly all private aircraft are required to have emergency locating transmitters to send out signals so rescuers can find the aircraft or wreckage if something goes wrong, said Ian Gregor, spokesman for the Federal Aviation Administration.

Unfortunately, the transmitter can be damaged and may not function because of impact or water, Gregor said.

The emergency locator transmitters in some cases have been active for three or four days, but that depends on the type of transmitter the Cessna has, said Coast Guard Lt. John Titchen.

"Generally how it works is the signal is constant, and so we are considering other options here in terms of trying to listen for it, but we're hopeful that we will find it as we continue flying the rest of today," he said.

3 INCIDENTS IN 4 YEARS

The missing plane was the third incident involving Island Hopper aircraft in a little over four years.

An Island Hoppers pilot and two passengers were seriously injured on April 18, 2004, when their Piper Warrior tour plane struck a hillside near Miloli'i on the Big Island and caught fire.

The National Transportation Safety Board found that pilot Jelica Matic had flown around the Big Island fewer than a dozen times before the accident and was relatively inexperienced with the aircraft she was using.

Matic told investigators the Island Hoppers plane was forced down by a powerful downdraft. She and her two passengers suffered burns from the fire.

On April 16 this year, another Island Hoppers flight carrying six tourists made an emergency landing on a highway about a mile from Kalapana, but no one was injured in that incident.

A statement from Island Hoppers yesterday said all appropriate agencies were notified after the flight disappeared.

"As all of our efforts and thoughts are focused on the safe return of our passengers and pilot, we appreciate the press media's concern and patience. We will issue further statements as information becomes available," Island Hoppers general manager Wendy Hart said in a written statement.

'WE'RE HOPEFUL'

Up to a dozen aircraft joined ground crews in the search yesterday, hunting across a search grid centered roughly on the last known position of the plane near Kilauea, the Coast Guard's Titchen said. Searchers also studied the routes Island Hoppers pilots customarily follow on company tours to focus on that path as well, he said.

The company routinely flies its tours clockwise around the perimeter of the Big Island, leaving Kona, passing over North Kohala, traveling down the Hamakua Coast through Hilo before circling the Hawai'i Volcanoes National Park area. From there, the flights generally pass over the Ka'u and South Point area before traveling north back to Kona.

"We've got a pretty good idea of where they could be, and that's what we're looking at now," Titchen said at midday yesterday. "We searched that route, (the fire department) has searched that route, and in addition, we've scoured the area around the last known position."

The weather for the search has been excellent, and "we're hopeful, and the search will continue for as long as we have a reasonable search area and good conditions," Titchen said.

The search included the Coast Guard C-130, a Coast Guard Dolphin HH-60 helicopter, and the two Big Island Fire Department Helicopters and six other aircraft from various tour companies including Blue Hawaii, Mauna Loa Helicopters and Island Hoppers, according to the Coast Guard and Big Island Civil Defense.

The Coast Guard began its search after being notified of the missing plane at about 3:15 p.m. Tuesday, and had aircraft searching continuously into last night.