The search for missing Malaysia Airlines flight MH370 is the “most challenging” ever seen, the man responsible for co-ordinating the search from Australia says.
Air Chief Marshall Angus Houston also said that the search for the plane could take weeks.
The plane disappeared on 8 March as it was travelling from Kuala Lumpur to Beijing. It was carrying 239 people.
Search teams are scouring the southern Indian Ocean for signs of the plane.
Speaking on Tuesday, ACM Houston, who is heading a new Joint Agency Coordination Centre (JACC) managing the search, said the task was “very complex” because the teams had no hard information to work from.
Search efforts would take time, he said. “It’s not something that will necessarily be resolved in the next two weeks, for example.”
Ten military aircraft and nine ships were scheduled to examine Tuesday’s search zone, while an Australia defence vessel with a towed pinger was en route to the area, he added.
It is now more than three weeks since flight MH370 disappeared. Malaysian authorities say that based on satellite data they have concluded that it crashed into the southern Indian Ocean.