PERTH, Australia —
Five planes, including three P-3 Orions, made the trip Friday. While search conditions had improved from a day earlier, with much better visibility, the Australian Maritime Safety Authority said there were no sightings of plane debris.
Searchers relied mostly on trained spotters aboard the planes rather than radar, which found nothing Thursday, Australian officials said. The search will focus more on visual sightings because civilian aircraft are being brought in. The military planes will continue to use both radar and spotters.
"Noting that we got no radar detections yesterday, we have replanned the search to be visual. So aircraft flying relatively low, very highly skilled and trained observers looking out of the aircraft windows and looking to see objects," said John Young, manager of the maritime safety authority's emergency response division.
Malaysia asked the U.S. for undersea surveillance equipment to help in the search, said Rear Adm. John Kirby, a Pentagon spokesman. Defense Secretary Chuck Hagel promised to assess the availability of the technology and its usefulness in the search, Kirby said.
The Pentagon says it has spent $2.5 million to operate ships and aircraft in the search and has budgeted another $1.5 million for the efforts.
There is a limited battery life for the beacons in the cockpit-voice and flight-data recorders — about 30 days, said Chuck Schofield, vice president of business development for Dukane Seacom Inc. He said it's "very likely" that his company made the beacons on the missing jet.
The devices work to a depth of 20,000 feet, with a signal range of about two nautical miles, depending on variables like sea conditions. The signals are located using a device operated on the surface of the water or towed to a depth.
Experts say it is impossible to tell if the grainy satellite images of the two objects — one 24 meters (almost 80 feet) long and the other measuring 5 meters (15 feet) — were debris from the plane. But officials have called this the best lead so far in the search that began March 8 after the plane vanished over the Gulf of Thailand on an overnight flight to Beijing.