A senior Malaysia Airlines executive said on Wednesday that the airline has "no reason to believe" that any actions by the crew caused the disappearance of the Boeing 777 over the weekend.
The search for the jet expanded further into the Andaman and South China Seas on Wednesday, with authorities no closer to explaining what happened to the plane or the 239 people on board.
With no concrete evidence to explain the plane's disappearance, authorities have ruled nothing out.
Police have said they were investigating whether any passengers or crew on the plane had personal or psychological problems that might shed light on the mystery, along with the possibility of a hijacking, sabotage or mechanical failure.
Hugh Dunleavy, the commercial director of Malaysia Airlines, said the captain in charge of the flight was a very seasoned pilot with an excellent record.
"There have been absolutely no implications that we are aware of that there was anything untoward in either his behavior or attitude," Dunleavy told Reuters news agency.
"We have no reason to believe that there was anything, any actions, internally by the crew that caused the disappearance of this aircraft."
Dunleavy said he was skeptical of a report by a South African woman who said the co-pilot of the missing plane, Farid Ab Hamid, had invited her and a female companion to sit in the cockpit during a flight two years ago, in an apparent breach of security.
"Because just getting into that area requires you to go through the secure doors that we have in the cabin all the time," he said.
"And not only would that have been unusual, but it also would have meant you'd have to walk by our cabin crew as well, and have the code to get through. So I'm dubious, but I'm going to let the authorities investigate and tell us what happened."
The airline earlier said it was taking seriously the report by the woman, Jonti Roos, who said in an interview with Australia's Channel Nine TV that she and her friend were invited to fly in the cockpit by Fariq and the pilot of a flight between Phuket and Kuala Lumpur in December 2011.
The TV channel showed pictures of the four apparently in a plane's cockpit.
The airline will give USD$5,000 per passenger to cover hotel expenses of relatives awaiting news, Dunleavy added.
The relatives, who have been staying at hotels near Beijing airport since the plane went missing on Saturday, have angrily accused the airline of keeping them in the dark. Malaysia Airlines said at least 152 of the 227 passengers on flight MH370 were Chinese.