The father of airman Corrie McKeague has said that his son is “no longer missing” as he claims he knows what happened to him and that he is in the waste disposal system.

Martin McKeague wrote on Facebook: “Corrie is no longer missing.

“What we mean by this is that after looking at all of the facts and evidence we now know what happened to our son.

“We are certain he is somewhere in the Suffolk waste disposal system, but his remains are essentially irretrievable.”

READ MORE: Police investigating RAF gunner's disappearance launch fresh appeal

Corrie McKeague was 23 years old when he vanished on a night out in Bury St Edmunds, Suffolk, on September 24, 2016.

Police believe he climbed into a waste bin and was taken away by a refuse lorry.

He had been stationed at RAF Honington, around 10 miles from Bury St Edmunds.

No trace of him has been found, and police said in March that the investigation was being handed to a cold case squad.

READ MORE: Investigation into missing RAF man Corrie McKeague has cost £2.1m to date

His father Martin McKeague wrote that police came to visit the family in Scotland to review the facts of the investigation in detail in October last year and February this year.

The evidence presented to him was “as thorough as it was compelling”, he said, and that experts “concluded beyond any doubt that Corrie had ended up in the Suffolk waste disposal system”.

“Accepting that conclusion has clearly not been easy for the McKeague family in Scotland, nor anyone else,” he wrote.

He said the remaining areas were either “too toxic to search” or “so vast it could take years to do so”.

He added that his son’s disappearance had been an “unbelievable and horrific journey of grieve (sic) and acceptance for the McKeague family”.

READ MORE: Mother of missing Corrie McKeague says traumatic childhood incident changed him

He said there are plans for a memorial for Corrie in the future.

When it emerged in March that the investigation would be handed over to a cold case squad, Suffolk Constabulary said officers had been through all realistic possibilities in detail and that there was no evidence of foul play.

Police carried out two searches of a landfill site at Milton, near Cambridge, last year, with the first search lasting 20 weeks and the second, lasting seven weeks, concluding in December.