PERTH: Search planes scoured a remote patch of the Indian Ocean but came back empty-handed Friday after a 10-hour mission looking for any sign of the missing Malaysia Airlines jet, another disappointing day in one of the world’s biggest aviation mysteries.

Australian officials pledged to continue the search for two large objects spotted by a satellite earlier this week, which had raised hopes that the two-week hunt for the Boeing 777 that disappeared March 8 with 239 people on board was nearing a breakthrough.

But Australia’s acting prime minister, Warren Truss, tamped down expectations.

“Something that was floating on the sea that long ago may no longer be floating — it may have slipped to the bottom,” he said. “It’s also certain that any debris or other material would have moved a significant distance over that time, potentially hundreds of kilometers.”

In Kuala Lumpur, where the plane took off for Beijing, the country’s defense minister thanked more than two dozen countries involved in the search that is stretching from Kazakhstan in Central Asia to the southern Indian Ocean, and said the focus remains on finding the airplane.

“This going to be a long haul,” Hishammuddin Hussein told a news conference.

The search area indicated by the satellite images — some 2,500 km southwest of Perth — is so remote it takes aircraft four hours to fly there and four hours back, leaving them with only enough fuel to search for about two hours.

On Friday, five planes, including three P-3 Orions, made the trip. While search conditions had improved from Thursday, with much better visibility, the Australian Maritime Safety Authority said there were no sightings of plane debris.