Milne told express.co.uk: "So now we have an 'extra' person on board MH370."
He added: "The extra passenger likely acted in conjunction with larger external operational support to take full command and control of the cockpit of MH370."
A spokesman for the MH370 safety investigation team said: "We are aware of this discrepancy. The actual number of passengers on-board was 227."
He said the manifest, which listed 228 passengers, was actually a computerised load sheet which was transmitted about two hours before the aircraft's departure.
"The actual figures can differ from that transmitted on the load sheet due to last minute changes," he said.
A lawsuit filed against Boeing in a US District Court in South Carolina, names seven malfunctions, from an electrical fire to depressurisation of the plane's cabin, that could have led to the crew losing consciousness, the plane's transponder stopping its transmission and the plane flying undetected until it crashed after running out of fuel.
The suit was filed by Gregory Keith, a special administrator for families who lost loved ones on the flight. It names 44 victims as plaintiffs.
The lawsuit was filed in South Carolina because Boeing has built a massive new plant in the state to build the 787 Dreamliner.
The lawsuit notes that search efforts for the plane have ended and says the lack of finality has led to unprecedented levels of "economic and non-economic losses, emotional and physical pain, distress and mental pain and suffering" for the people on the airliner and their families. It does not ask for a specific amount of damages.
The lawsuit also says Boeing did not use technology which is available that would have allowed it to be tracked at all times and made the flight and cockpit voice recorders easier to find.
Boeing knew of design flaws on the aircraft, including defective wiring near combustible sources like the emergency oxygen supply to the plane's crew, says the lawsuit.
The lawsuit goes on to say: "The defects caused and/or allowed a massive and cascading sequence of electrical failures onboard the lost plane which disabled vital systems ... making it impossible for the crew to navigate the plane or for the plane to communicate with the ground stations leaving the aircraft to fly without the ability to communicate or control the aircraft until the plane ran out of fuel."
In March last year 12 Chinese families whose relatives were aboard the flight filed a lawsuit in Beijing.
It also named Boeing and jet engine manufacturer Rolls-Roys among the defendants.
Another lawsuit on behalf of the families of 32 passengers was filed in Kuala Lumpur.
A Malaysian woman and her two young sons also sued the airline, seeking damages of $7.6million for the loss of her husband, S Puspanathan.
An Australian-based woman, Jennifer Chong, whose husband Chong Ling Tan was on the flight, filed similar claims in Australia, alleging the airline was negligent in failing to ensure passengers' safety.
The families of four more Australian passengers are seeking $200,000 (£165,000) compensation from Malaysia Airlines, according to documents filed in the Federal Court of Australia in April 2016.
In June 2016, two Malaysian boys whose father, Jee Jing Hang, was a passenger secured an out-of-court settlement in the first legal case against Malaysia Airlines and the government.
Boeing spokesman Tom Kim said it does not comment on pending lawsuits but the company said its thoughts remained with the people who died on Flight MH370.
