Evidence in the inquiry into missing airman Corrie Mckeague was manipulated, his mother has claimed.
Nicola Urquhart believes there was "inconsistency" over raw data on the weight of a bin load taken to landfill in the hours after he disappeared.
She appeared on the BBC's Victoria Derbyshire show following Suffolk Police's decision to end the investigation into his disappearance.
The force said it had faith in the information given.
A Suffolk Police spokesman said: "Following extensive inquiries, we have absolute confidence in the raw data provided to us by Biffa which identified the time, date and the weight of the bin concerned which was unusually and excessively heavy."
However, Mrs Urquhart has said the data had either been manipulated or "someone is lying" to the police.
Investigators were initially given the wrong weight of the bin that Mr Mckeague may have climbed into, making it too light to support the theory he was in there.
This was later corrected, showing that the bin was actually much heavier than first thought.
The force said evidence "still points to Corrie being transported from the 'horseshoe' area in a bin lorry and ultimately taken to the Milton landfill site".
Mr Mckeague, originally from Dunfermline and serving at RAF Honington in Suffolk, disappeared after a night out in Bury St Edmunds on 24 September 2016, when he was 23 years old.
Mrs Urquhart, who appeared on the BBC show alongside Corrie's brothers, Makeyan and Darroch, said: "I have looked at this raw data… there is an inconsistency.
"The raw data has either been manipulated or someone is lying about what they have told the police.
"They have been prepared to spend £2m… they should be arresting people and questioning them under caution.
"Their data does not match what they have been told."
In a subsequent interview with BBC Look East, Mrs Urquhart said police had promised to provide her with the raw data.
What she had been shown before had been "packaged" by either the force or the bin firm, she said, and was not a copy of the original records.
She also said police had told her a witness "opened that bin and looked inside it and did not see Corrie" and said it remained possible he could have left the area by car or on foot.
The force spent 28 weeks trawling the Cambridgeshire landfill site for the missing airman's remains and said it was "content" Corrie was not there.
But Mrs Urquhart, an officer with Police Scotland, said the family was still determined to find out what happened to him.
"We will not give up until we have reasonable answers to reasonable inquiries," she said.
"It is not good enough for a police officer of rank to turn round and say to me 'sometimes you just can't get answers'," she later told BBC Look East.
"If I sat here and listed everything we haven't been given an update about, people would probably be horrified.
"The rug has been pulled out from underneath me again and a decision made which is just so wrong."
Although there have been no recent sightings of Corrie, Mrs Urquhart said she would now work with Suffolk Lowland Search and Rescue to pinpoint any places he had been spotted or areas not already scoured.
Mrs Urquhart and her sons also rejected claims by Corrie's father Martin Mckeague that he was depressed after finding out his girlfriend was pregnant.
April Oliver announced in June the gunner had become a father with the birth of their daughter.
"Corrie did not know, it had not been confirmed and he was not depressed," said Mrs Urquhart.
On Monday, Det Supt Katie Elliott confirmed the search for Mr Mckeague was being scaled back.
"We have now reached a point where we are unable to make any further progress, and have gone as far as we realistically can with the information we have," she said.
However, Mrs Urquhart told the programme: "I don't want to come on here and just criticise the police, but - and it may be that we get to the same point as they are - they've turned this over to a cold case before they've looked at all the information."
Mr Mckeague has said to the Cambridge News he was planning a memorial service for his son in Scotland and understood RAF Honington would also be holding a service.