Co-pilot Fariq Abdul Hamid has come under intense scrutiny, along with Captain Zaharie Ahmad Shah, after Malaysian authorities said flight MH370's disappearance was due to "deliberate" action in the cockpit.
However, nothing has yet emerged publicly to implicate the two men.
The flag carrier said Fariq, 27, had come through his initial outings in the 777 model with no issues under a standard arrangement in which a First Officer's first five flights in a new model of plane are done under the watchful eye of a "check co-pilot".
"The first five flights, the co-pilot normally flies with what we call the check co-pilot. He actually passed the first five flights. We do not see any problem with him," the airlines' chief executive Ahmad Jauhari Yahya told a daily press conference on the crisis.
Flight 370 disappeared off civilian radar about an hour into its journey from Kuala Lumpur to Beijing carrying 239 people, sparking an unprecedented international search across huge swathes of the Indian Ocean and South China Sea.
Ahmad Jauhari added that Zaharie, 53, was himself an experienced 777 examiner.
"You must realise that he (Fariq) is flying with an examiner. The captain is a 777 examiner," he added, referring to Zaharie.
Aircraft and ships from several nations are zeroing in on suspected plane debris in the southern Indian Ocean, but have been prevented from recovering anything for confirmation due to the distances involved and rough weather.
Fariq, who joined Malaysia Airlines seven years ago, was accused in an Australian television report of allowing two young South African women into the cockpit of a plane he piloted in 2011, breaching rules imposed after the 9/11 attacks in America.
Police also removed a flight simulator from Zaharie's home and were examining it for any clues.