Malaysia Airlines did not meet its own rules for tracking the location of lost Flight MH370 while it was in the air, a new book has claimed.
The Boeing 777, which was carrying 239 passengers and crew, disappeared en route from Kuala Lumpur to Beijing.
Investigators have still not determined the exact course the plane took on March 8, 2014, or recovered all the wreckage.
Now, in The Crash Detectives, journalist Christine Negroni has accused the Kuala Lumpur-based carrier of failing to ensure the doomed aircraft was constantly tracked.
She wrote that company rules said the location of all aeroplanes should be monitored - by sending regular bursts of data to a controller on the ground - "through all phases of the flight".
But Negroni said a report by internal auditors, undertaken in April 2013, found the carrier's planes were not meeting this requirement and, by law, should not have been cleared to fly.
She also claimed that Malaysia's acting transport minister when the plane disappeared, Hishammuddin Hussein, knew about this audit but did not admit this to reporters.
Acting transport minister Hussein told a press conference convened two days after the flight disappeared that the government had "nothing to hide".
"The airline was informed by its own staff that it was unable to comply with tracking regulations," Negroni told thedailybeast.com.
Auditors reports seen by Negroni did not say how frequently aeroplanes should be tracked.
But she discovered that Malaysia Airlines' long haul flights now send tracking information every five minutes.
American lawyer Blaine Alan Gibson is carrying out a one-man investigation into the fate of MH370, and found a piece of wreckage from the aircraft in March.
An Australian-led operation is scouring the seafloor within a remote 120,000-square-kilometre belt of the Indian Ocean where authorities believe the passenger jet went down.
The search is nearly finished, however, and families are bracing for it to be called off.
MailOnline has contacted Malaysia Airlines for a comment.