Abbott didn't elaborate, and pleaded for patience from the families of the 239 people on board, some of whom believe the authorities are withholding vital details about the disappearance of their loved ones.
The Australian PM addressed the media alongside Malaysian counterpart Najib Razak after they were briefed on the search at the Royal Australian Air Force's base at Pearce, near Perth.
Yesterday eight aircraft and nine ships scanned a 238,000sq km area of sea about 1700km northwest of the West Australian capital.
Earlier, the leaders joined around 50 personnel for a morale-boosting breakfast as air crews prepared for another 11-hour shift.
In Malaysia, the focus of the investigation into why the Boeing 777 suddenly went "dark" shortly after takeoff from Kuala Lumpur on March 8 remains on the two pilots.
The country's most senior police officer, Khalid Abu Bakar, has reportedly cleared all 227 passengers - most of whom were Chinese - of involvement.
Investigators trying to solve one of aviation's most baffling mysteries still believe the Malaysia Airlines plane was deliberately diverted, but without solid evidence, are leaving open other areas of inquiry.
The latest in a mountain of theories is that food served on board may have been poisoned. Bakar said every possible angle had to be investigated to be ruled out.
Authorities are losing the race against time to find perhaps the most vital piece of evidence - the plane's "black box". A detector on board the Australian naval vessel Ocean Shield is expected to arrive in the search zone today. But the device will need to get within 1.5km to pick up a battery-powered signal that is expected to run out within the next few days.
While Abbott and Najib both described the search as without precedent, they spoke glowingly of the international co-operation.
"Differences have been set aside as 26 nations have united behind a common cause," said Najib, who described Australia as a "reliable and true friend".
