KUALA LUMPUR - One is a technical wizard whose affable manner made him a favourite of trainee pilots; the other an enthusiastic young aviator planning to marry his sweetheart.
The captain and co-pilot of Malaysia Airlines flight MH370 are now at the centre of a baffling paradox - as circumstantial evidence mounts that at least one of them may have been involved in the plane's disappearance on March 8, accounts of their lives portray them as sociable, well-balanced and happy.
Described as devoted to their families and communities, neither fits the profile of a loner or extremist who might have a motive for suicide, hijacking or terrorism.
International media scrutiny and investigations by the police have failed to turn up red flags on either the captain, 53-year-old grandfather Zaharie Ahmad Shah, or the co-pilot, 27-year old Fariq Abdul Hamid.
Both live in well-to-do neighbourhoods in Shah Alam, an area west of Kuala Lumpur that is popular among flight crews for its proximity to the international airport.
On Tuesday, security guards prevented reporters from entering Zaharie's upscale gated residence. About 10 minutes' drive away, Fariq's house stood empty, with an unread newspaper lying outside.
Family and friends say there is nothing in their personalities or past to suggest they would have committed foul play.
"I've never seen him lose his temper. It's difficult to believe any of the speculation made against him," said Peter Chong, a friend of Zaharie, describing him as highly disciplined and conscientious.
Eleven days after the Boeing 777 jetliner carrying 239 people vanished without trace, scrutiny has zeroed in on the pilots due to the deliberate way in which the plane was switched into radar darkness and diverted far from its route to Beijing.
The person who chose that exact time and place to vanish appears to have acted only after meticulous planning and must have had advanced aviation knowledge, according to experts.
"It raises so many questions, not least that you have got to be prepared to believe that a pilot would do this," said Paul Hayes, a leading air safety expert at British-based consultancy, Flightglobal Ascend.
"But it is hard to understand the motive. In cases where pilot suicide was thought to be the cause, the alleged suicide pilots executed the plan as soon as they were in a position to do so."