Richard Quest is CNN's Aviation Correspondent and author of "The Vanishing of Flight MH370," a new book that examines the flight's disappearance, two years on. The opinions in this commentary are his.

(CNN) Two years after MH370 went missing and key questions remain unanswered: Where is the plane and what happened in the cockpit in the early hours of March 8, 2014?

Amid the conspiracy theories, there are two main views on what might have happened.

The first suggests that the captain hijacked the plane and flew it with all 238 other people on board to their deaths by crashing in the southern Indian Ocean.

The second view, and the one to which I subscribe, is that there was some form of mechanical fault.

Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said.

Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said.

Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014.

Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014.

A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014.

A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014.

Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014.

Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014.

The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014.

The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014.

Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014.

Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014.

A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand.

A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand.

A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014.

A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014.

A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014.

A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014.

Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014.

Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014.

Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean.

Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean.

On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet.

On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet.

A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014.

A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014.

Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight.

Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight.

Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search.

Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search.

A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia.

A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia.

Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived."

Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived."

A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014.

A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014.

The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions.

The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions.

On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370.

On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370.

A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014.

A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014.

A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014.

A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014.

A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014.

A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014.

The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014.

The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014.

A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014.

A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014.

Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014.

Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014.

Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public.

Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public.

A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane.

A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane.

Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead.

Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead.

In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was.

In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was.

Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft.

Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft.

On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight.

Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board.

Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board.

Under that scenario, the pilots tried to get back to safety in Malaysia, but became incapacitated and the plane flew on; or that the pilots are heroes, and knowing they were doomed, set a course to avoid ground casualties and died after the plane crashed.

The simple, short answer as to which is true: we don't know. Anyone who tells you they do know is, frankly, making it up.

Rogue pilot?

The pilot theory pins the probable blame on 53-year old captain Zaharie Shah. I don't agree for a variety of reasons.

Pilot suicide is incredibly rare. When it happens it is shocking and deeply troubling for the traveling public. The most recent of course was the horrible crash of Germanwings 9525 in March 2015, where the first officer, Andreas Lubitz locked the captain out of the cockpit, then reset the autopilot altitude to 100 feet sending the plane crashing into the French Alps.

Whether premeditated (as the evidence shows with Germanwings) or on the spur of the moment, the deranged mind doesn't spend hours carefully plotting flight plans, working out how to disconnect every communication tool on the aircraft, then flying elaborate routes around countries ostensibly to avoid military radars. No -- they take over the aircraft and crash the plane. MH370 doesn't fit this pattern. And so far I can't find any case that would suggest it does.

With pilot suicide cases, we tend to find out the potential reasons relatively quickly. With Germanwings, we found out almost immediately the psychological and medical issues suffered by Lubitz. He had been doctor shopping in the weeks before the crash, visiting numerous general practitioners, psychologists. He had ripped up sick notes in his apartment and had been researching online suicide methods and the locking mechanism of the cockpit door.

Insufficient evidence

With MH370, we have no real evidence. None whatsoever. We have a few rumors, a bit of gossip and a few circumstantial facts which some wish to string together to make a case against the pilots.

MH370 pilots: First officer Fariq Abdul Hamid (left) and Captain Zaharie Ahmad Shah (right).

Let us not forget Captain Zaharie had been a pilot with Malaysian airlines since 1981. He was a captain on the 777 for more than 15 years. He was exceptionally experienced -- a training captain -- who had been paired with 27-year-old first officer Fariq Ab Hamid. Hamid was transitioning to the 777 fleet and this was one of his first 777 flights out of the simulator on the real metal. Hamid was engaged to be married to a pilot at another airline.

The Factual Report published on the first anniversary of the plane's disappearance actually goes so far as to dismiss these accusations. It says, "the captain's ability to handle stress at work and home was good. There were no significant changes in his life style, interpersonal conflict of family stresses."

I am not naïve and obviously can see that the Malaysians might want to put the "best face on" to protect the reputation of their country's pilots. But we have to take the report at face value -- it's all we have on the record.

In the absence of that hard evidence, alternative theories flourished, bolstered by rumors. Like how the captain circled his home island of Penang for "one last look," or how the plane flew at different altitudes and routes to avoid radar. These make good yarns but aren't true.

Photos: Remembering the passengers of MH370 Photos: Remembering the passengers of MH370 There is still no way to know for sure why Flight MH370 ended, but we are learning more about the lives of those on board. CNN is remembering them through snapshots shared with us. Hide Caption 1 of 12 Photos: Remembering the passengers of MH370 Rodney and Mary Burrows were looking forward to becoming first-time grandparents after their return home to Australia. Hide Caption 2 of 12 Photos: Remembering the passengers of MH370 Australians Catherine and Robert Lawton were traveling with friends on vacation when the flight disappeared. Hide Caption 3 of 12 Photos: Remembering the passengers of MH370 Paul Weeks was traveling to Mongolia for a new job as an engineer. His wife says Paul left behind his watch and his wedding ring before the trip, in case anything happened to him while he was away. Anderson spoke with Paul's brother & sister who said they are coping by spending time together as a family. Hide Caption 4 of 12 Photos: Remembering the passengers of MH370 Chandrika Sharma, left, was on Flight 370; her daughter Meghna and husband K.S. Narendran wait patiently, trying to manage their anxiety and longing for her return. Hide Caption 5 of 12 Photos: Remembering the passengers of MH370 Muktesh Mukherjee and Xiaomo Bai had been vacationing in Vietnam and were on their way home to their two young sons in Beijing. Hide Caption 6 of 12 Photos: Remembering the passengers of MH370 76-year-old Liu Rusheng, an accomplished calligrapher and one of the oldest passengers on the flight, was in Malaysia to attend an art exhibition with his wife. Hide Caption 7 of 12 Photos: Remembering the passengers of MH370 Teens Hadrien Wattrelos and Zhao Yan are shown in a photo on Wattrelos' Facebook page. The photo is captioned, simply, "I love you," in French. Hide Caption 8 of 12 Photos: Remembering the passengers of MH370 Firman Chandra Siregar, 24, studied electrical engineering in Indonesia and was on his way to Beijing on board Flight 370 to start a new job at an oil company. Hide Caption 9 of 12 Photos: Remembering the passengers of MH370 Patrick Francis Gomes, center, was the in-flight supervisor for the missing plane. His daughter describes him as a quiet person with a sense of humor. Hide Caption 10 of 12 Photos: Remembering the passengers of MH370 Ch'ng Mei Ling, a Malaysian citizen who lives in Pennsylvania, is a process engineer at a chemical company. Hide Caption 11 of 12 Photos: Remembering the passengers of MH370 We do not have photos of all 239 passengers, but we wanted to remember that there are loved ones around the world missing them right now. View CNN's complete coverage of Flight 370. Hide Caption 12 of 12

There was no circling of Penang and there was no major change in altitude -- the Malaysian radar turned out to be wrong. These theories were all debunked by the Australian Transport Security Bureau in a rebuttal to Australian veteran pilot Byron Bailey who argues for the "rogue pilot" theory.

Also, the plane was spotted by Thai radar, which ignored it because it wasn't relevant. Finally, never forget that the plane was spotted by the Malaysian military as it flew across the country on that fateful night but was also ignored. A rogue pilot couldn't have banked on the failure of an oblivious radar operator not to scramble jets to see what was going on.

I shall leave it to others to make the case against the pilots on technical grounds. But we must stick to the facts.

The fact is there is no evidence to say the pilots did this.

Before I am prepared to convict a lifelong captain or a newbie first officer of hijacking a plane and killing 238 other people, I want more than a few odd rumors, a lot of scurrilous gossip and a heap of poor arguments. I am prepared to be proved totally wrong. Until such time I am not prepared to say "it was the pilot that did it."