Malaysian Transport Minister Hishammuddin Hussein said Tuesday the international land and sea search area is currently around 7.68 million square kilometers (2.24 million nautical square miles).
He told a news conference the "unique, unprecedented" search extended from central Asia to the southern Indian Ocean.
It covers two huge arcs north and south of the area from where last contact was made.
Twenty-five countries are now helping to hunt for the plane, which disappeared on March 8 en-route to Beijing with 239 people on board.
Intelligence services are yet to determine the fate of the plane, with speculation rising over a possible hijacking.
Malaysian authorities say someone on board the flight switched off two vital pieces of communication equipment, allowing the plane to fly almost undetected.
As a result, the investigation has zeroed in on the plane's captain, Zaharie Ahmad Shah, and his co-pilot Fariq Abdul Hamid, with the key question being about the identity of the person in control of the plane when it veered off-course about an hour after takeoff.
The continued uncertainty has enraged anxious relatives who still know little about the fate of their loved ones.
On Tuesday a group of relatives of some of the Chinese passengers in Beijing said they planned to start a hunger strike to protest the handling of the investigation.
They allege that Malaysian authorities are holding back information and have demanded more clarity.
ccp/rc (AFP, Reuters, AP)