Nicola Urquhart, 48, has posted a picture of him on exercise in France in June 2016 along with a touching message.
She said: "He called after spending a night in sand dunes freezing saying he was physically exhausted, the next night he called saying 'This was the best job in the world' he'd completed the exercise along with his colleagues and I could hear the pride in his voice.
The new image shows Corrie McKeague in a training exercise in France
Corrie's mum Nicola thanked the public for the support they have shown
We've been pushed close to our limits
"Only 2 days left of searching this week. We've been pushed close to our limits, waiting for the phone to ring over the last 9 days, we will get through this tho, the kindness and support in every private or public message is still overwhelming, but honestly it's never been appreciated more."
Police are currently scouring a landfill site in Milton, Cambridgeshire, for missing Corrie and say they have a "great deal of confidence" that he will be found there.
He went missing after a night out in Bury St Edmunds, Suffolk on September 23.
MISSING RAF serviceman, Corrie Mckeague Mon, January 9, 2017
Corrie Mckeague, of Dungermline, Fife, has been missing since he disappeared after a night out in Bury St Edmunds, Suffolk on September 24. The 23-year-old's girlfriend, April Oliver, 21, of Norfolk, revealed she found out she was expecting his child two weeks after he vanished near RAF Honington where he has been based for three years while training to be a gunner and a medic.
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April Oliver, 21, girlfriend of missing 23-year-old Corrie McKeague (right), who has revealed she is expecting his child
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Corrie went missing after a night out in Bury St Edmunds
Police were led to the waste tip site after records showed that a rubbish lorry collecting refuse bins in the area had picked up a heavier load than expected.
The search for Corrie McKeague has now cost police services more than £750,000 – which is one of the most expensive missing person investigations of all time.