Head of recovery effort warns that hunt could 'drag on for a long time'

Even as a vessel equipped with a specialized black-box "pinger" locator raced against the clock to reach the Indian Ocean search area, Australia cautioned on Tuesday that the hunt for the missing Flight MH370 could be long and frustrating.

No wreckage has been found since the Malaysia Airlines jet vanished on March 8, despite an extensive multinational search effort southwest of Perth.

Recovery of the aircraft's flight recorder would provide crucial understanding about what happened to the flight, but the so-called black box has limited battery life and the search area remains large. Without some means of narrowing the area, such as the discovery of crash debris, the chances of finding the black box are remote, experts have said.

Ten planes and nine ships were involved in Tuesday's search for the missing flight, the Joint Agency Coordination Center announced from Australia.

The coordination center was established on Monday and is being led by retired Air Chief Marshal Angus Houston in Perth to effectively coordinate the Australian government's search and recovery operation.

The 10 planes, including a Chinese Ilyushin IL-76, two Australian air force P3 Orions, two Malaysian C-130s and a US navy P8 Poseidon, will assist in the search, with a civil jet providing communications relay.

Nine ships have been tasked to search in four separate areas. Australian defense vessel Ocean Shield departed HMAS Stirling, a base on Australia's west coast, on Monday night, with the pinger locator.

Houston, the coordination center chief, said it was the most challenging search-and-recovery operation he had seen and cautioned about quick fixes.

"I say that because the starting point is the last known position of the vehicle or aircraft. In this particular case, the last known position is a long, long way from where the aircraft appears to have gone," he said.

"This could drag on for a long time, but I think at this stage it's very important to pursue all leads."

The captain of the Chinese vessel Haixun 01, Jiang Long, told Xinhua on Tuesday that Chinese ships have ruled out floating objects as being related to the flight in 11 locations in the search area where suspicious objects had been seen by aircraft observers or satellites.

Malaysia's civil aviation department made a correction late on Monday, saying that the last words spoken by one of the pilots of MH370 were "Good night, Malaysian three seven zero", and not the more casual "All right, good night" that was originally reported.

"The authorities are still doing a forensic investigation to determine whether those last words from the cockpit were by the pilot or the co-pilot," the department said.

The new admission is likely to add to criticism of the Malaysian authorities' handling of the incident.

Families of the 154 Chinese passengers on the missing plane, who had been particularly scathing in accusing Malaysia of incompetence and even a coverup, said earlier this week that they had also received much help and warm wishes from across the world. They expressed gratitude for all those involved in the search.

Tourist arrivals from China have dropped since the tragedy, Malaysia's Tourism and Culture Minister Mohamed Nazri Abdul Aziz said. But he said he is confident that the airline crisis will not affect arrivals from other countries. The ministry is redoubling its efforts to promote Malaysia to markets elsewhere, several Malay dailies reported on Tuesday.