With the angle of terrorism linked to two Iranian men carrying stolen passports ruled out after it appeared they were economic asylum seekers, Malaysian authorities are now looking into the 237 other passengers and crew of the ill-fated Malaysian Airlines Flight 370 for clues to the plane's whereabouts.
One passenger they are focused on is a 35-year-old Chinese Ughur man with flight simulation training, Harian Metro, a leading Malay language newspaper in Kuala Lumpur, reported on Thursday.
The daily said the man was a PhD degree holder from a British university and recently was a lecturer at a university in Turkey. He studied flight simulation in Sweden in 2006.
The Ughurs are Muslim ethnic minority groups in Xinjiang, a northwestern Chinese province, who have been seeking independence since the Chinese took control of the area in 1949. They claim being oppressed by the Chinese government and religious restrictions too.
The Ughurs are being blamed for a violent attack at a Chinese train station.
Could it have links to the Chinese Martyr's Brigade which sent an email to Chinese media and claimed it was behind the disappearance of the plane? The email warned, "You kill one of our clan, we will kill 100 of you as payback," although Malaysia believes it is a hoax.
The Malaysian police are also checking the background of the crew and had raided the house of chief pilot Zaharie Ahmad Shah, questioning his family over the pilot's behaviour the past few days prior to the ill-fated flight.
Personal differences among the crew is one of the angles the investigators are looking into, said Inspector-General of Police Tan Sri Khalid Abu Bakar, besides sabotage and hijack as the reasons behind the Boeing 777 jet's disappearance with so far no traces left.
Les Abend, an aviator with 29 years of flying experience in Boeing 777 jets as captain discussed with CNN the possibilities behind the plane's disappearance, including a fuel tank explosion.
His conclusion is that a plane would not fall out of the sky because of only one factor since aviation mishaps involve multiple factors. Airplanes, Mr Abend insisted, "Just don't disappear."