Inspector-General of Police Tan Sri Khalid Abu Bakar, said an examination of the simulator, taken from the home of pilot Zaharie Ahmad Shah, 53, showed its data log had been cleared on Feb 3, more than a month before the airliner, carrying 239 people, disappeared on a flight from Kuala Lumpur to Beijing.
No wreckage has been found from the jetliner, which vanished from air traffic control screens off Malaysia's east coast at 1.21am on March 8, less than an hour after taking off.
Malaysia has now made available to the FBI electronic data generated by both pilots of Flight MH370, including data from a hard drive attached to the captain's flight simulator, and from electronic media used by the co-pilot, Fariq Abdul Hamid, a US law enforcement official told Reuters.
The official said he could not confirm that some data had been wiped from the simulator and stressed that there was no guarantee the FBI analysis would turn up any fresh clues.
The FBI has extensive experience investigating airplane crashes, including those of TWA 800 and EgyptAir 990 off the US east coast in the 1990s and Pan Am Flight 103 over Lockerbie, Scotland.
In the case of EgyptAir 990, the FBI helped air safety investigators establish that the crash was caused by a suicidal co-pilot, while in the case of Pan Am 103, the agency worked with British and US intelligence to build a case against the government of Libya.
The unprecedented search for the Boeing 777-200ER had focused on two vast search corridors: one arcing north overland from Laos towards the Caspian Sea, the other curving south across the Indian Ocean from west of Indonesia's Sumatra island to west of Australia.
"The working assumption is that it went south, and furthermore that it went to the southern end of that corridor," said a source close to the investigation.
That view is based on the lack of any evidence from countries along the northern corridor that the plane entered their airspace, and the failure to find any trace of wreckage in searches in the upper part of the southern corridor.
Some sources involved in the investigation have voiced fears it could stall due to the reluctance of countries in the region to share militarily sensitive radar data that might shed new light on the direction the jet took.
Malaysian and US officials believe the aircraft was deliberately diverted perhaps thousands of miles off course, but an exhaustive background search of the passengers and crew aboard has not yielded anything that might explain why.
If the plane did indeed end up in the southern Indian Ocean, one of the remotest places on Earth and also one of the deepest seas, it increases the chance it may never be found - and investigators may never know for sure what happened on board.
Officials believe that someone with detailed knowledge of both the Boeing 777 and commercial aviation navigation switched off two vital datalinks: the ACARS system, which relays maintenance data back to the ground, and the transponder, which enables the plane to be seen by civilian radar.
US agencies have looked for evidence that anyone other than the pilots knew how disable ACARS but have found nothing. - Reuters