The Air Accident Investigation Branch is due to publish its final report into the plane crash that killed footballer Emiliano Sala and pilot David Ibbotson.
Investigators in charge of the report have already revealed the pilot was not licensed to conduct commercial flights and that Sala was exposed to high levels of carbon monoxide prior to the crash.
The Argentinian striker was flying from Nantes in France to Cardiff when the Piper Malibu aircraft crashed into the English Channel, near Guernsey on January 21 last year.
An extensive air and sea search followed that saw over 1,700 square miles covered. This search was called off after three days with rescuers failing to find any sign of the plane.
A private underwater search was launched after £300,000 was raised by the Sala family in a fundraising campaign.
The Piper Malibu aircraft was found on the seabed just 30 metres from where the final radar reading located it.
Mr Sala’s body was recovered but pilot Ibbotson has still not been found.
The decision was taken not to recover the aircraft wreckage from the ocean floor.
A coroner’s report found that Sala had died from "head and trunk injuries."
An interim report published by the Air Accidents Investigation Branch shortly after the accident said pilot Ibbotson was not licensed to conduct commercial flights.
It also raised further questions over the validity of Ibbotson’s license and confirmed it would be a focus of their investigations.
It was later revealed in a toxicology report that both Sala and Ibbotson had been exposed to harmful levels of carbon monoxide in the cockpit when the plane crashed.
Tests on the striker's body found enough evidence of the harmful gas to cause a heart attack, seizure or unconsciousness.
The AAIB said the gas was likely to have affected Mr Ibbotson’s “ability to fly an aircraft depending on the level of that exposure."
Sala was signed by Cardiff City from Nantes for £15m, but he never played for the club.
His death sparked a row between Cardiff and his former club over whether the transfer fee should be paid.
The then-Premier League club were ordered to pay the first instalment of Sala's £5.2m transfer fee in September 2019.
Cardiff appealed against the ruling and will go before a court in Switzerland. The final decision is not expected before June 2020.
Earlier this week police said a 64-year-old man arrested on suspicion of manslaughter over the death of Sala will face no further action.
The man from Yorkshire was arrested on June 19 last year. Dorset Police say they are continuing to support the investigation.