ANCHORAGE (AP) -- The Federal Aviation Administration has stepped up efforts to determine the source of wavering lights that dogged a Japan Air Lines cargo jet across Alaska's night sky for nearly an hour in November. "We're looking at it to ensure that somebody didn't violate airspace we control," FAA spokesman Paul Steucke said Sunday. "We looked at it about six weeks ago, but since then we've gotten a lot of public interest, so we went back and re-interviewed the pilot. He provided us with additional information."

Veteran pilot Kenji Terauchi told investigators Friday through an interpreter that two of the lights were small, perhaps no larger than eight feet across. He said the third light was on an aircraft, a huge darkened globe with a diameter of perhaps two aircraft carriers placed end-to-end, Steucke said.

The pilot said the large UFO showed up on his cockpit weather radar. But images on military radar screens at the time were dismissed as "clutter," and a blip that showed up on FAA screens was analyzed as a coincidental "split image" of the aircraft, Steucke said.

Radar tapes, transcribed interviews and radio messages are to be sent to the FAA in Washington, D.C., later this week for review, Steucke said.

A JAL spokeswoman Sunday said Terauchi was on a flight to Europe and was unavailable.

Flight 1628, with a three-man crew, left Iceland on Nov. 17 with a load of wine bound for Tokyo from Paris. Terauchi and his crew picked up the Boeing 747 in Iceland for the Polar leg of the flight to Anchorage.

The evening sky was clear as the jet, cruising at 525 knots, crossed into Alaska from Canada, just northeast of Fort Yukon. At 6:19 p.m. (AST), as the plane flew at 35,000 feet, Terauchi said he saw three lights eight miles in front of his aircraft.

The pilot reported the lights were yellow, amber and green, Steucke said, but not red, the international color for aircraft beacons.

"The two smaller ones moved a little bit, changed their angle. The smaller ones did not show up on the weather radar onboard," Steucke said. "The larger one did.

"It appeared to him it might be possible that the lights might be exhaust pipes, they kind of wavered but did not blink. His main concern was trying to determine whether he was overtaking another aircraft."

Steucke said the pilot reported he dimmed cockpit lights to ensure he was not seeing a reflection.

"He flew for about six minutes before he decided to report anything," Steucke said. "I can't say I blame him for that." Terauchi radioed Anchorage FAA air controllers, who direct all aircraft traffic in the state, except for planes near airports, Steucke said. Fairbanks controllers checked their screens but saw only Flight 1628, Stuecke said.

The pilot reported the object was staying with him and controllers told him to take any evasive action needed. Terauchi decreased altitude to 31,000 feet, but the lights went down with him "in formation," Steucke said.

South of Fairbanks, Terauchi turned the plane in a complete circle to see if the lights would follow. "That was pretty clever," Steucke said. "It allowed him to eliminate any natural phenomenon which would have stayed stationary."

The lights stayed with the cargo jet, and moved to its left side, the pilot told the FAA.

Friday, he told investigators that there were no magnetic disturbances noted on the plane and no changes in its instruments or navigation systems, Stuecke said.

The FAA in Anchorage and the military in Alaska use the same long-range radar in Fairbanks, Steucke said. The FAA also uses sophisticated computer systems to screen clutter before it reaches radar screens, he said.

The military in Alaska does not use such computers, he said. "The military decided about a minute into this exercise that what it was seeing was clutter," he said. The Air Force did not send up an interceptor and is not investigating the matter, Steucke said. At the FAA center in Anchorage, controllers following the flight noted occasional second blips, or "split targets," on the screen near Flight 1628, Steucke said.

"That happens when the transponder aboard the aircraft is not electronically in sync with radar bouncing off the plane," he said. "We get an intermittent blip every three sweeps of the radar screen. It's not unusual. It has happened and it does happen.

"It was what I call coincidence that the split image happened to fall at the right distance and the same side of the aircraft that the object was reported by the pilot."

The lights vanished, heading east, when the JAL jet was about 80 miles north of Anchorage, Steucke said.

The FAA has ruled out alcohol or drugs as a factor in the sightings, Steucke said. "They were rational, professional pilots. I'd describe them as very sincere, very intense," Steucke said.

"I've been here 12 years, I've been with the FAA three, and I've talked to people who've been here seven or eight years and they don't recall anything like this," he said.

The FAA started investigating the report after the sighting, he said, but not as a top priority. "Basically, the public interest heightened the interest level. I wasn't hiding it, but I wasn't standing on a rooftop announcing it," he said.