The private contractor that is hired to find Malaysia Airlines Flight 370 will have 300 days to complete an undersea search for the missing jetliner in the southern Indian Ocean.

Tender documents released by the Australian government outline for the first time the requirements of this phase in the search, the largest of its type in history. They also highlight continued uncertainty about the operation, including the seabed's terrain and the area to be scoured using sonar equipment.

The Australian Transport Safety Bureau said it hasn't fixed upon an exact search area because it is continuing to analyze satellite communications and calculations on the Boeing 777's likely performance.

The winning contractor faces aggressive deadlines to search an area of about 23,000 square miles. The plane dropped off radar March 8 with 239 people on board during a flight to Beijing from Kuala Lumpur.

The retooled search will cover a much larger region and is expected to use sonar technologies designed to scan wide swaths of ocean floor. The initial effort was focused on more-detailed examination of a smaller, prioritized area.