Sniffer dog teams and the Police Scotland helicopter are today helping to search for a 54-year-old man missing from Cupar.
Officers believe Gordon Johnstone, who works at RAF Leuchars, could be in the north east Fife, Dundee or the Carnoustie area.
The search, assisted by RAF personnel, has been concentrating on the Tentsmuir Forest area over the last few days.
It is understood that mobile phone signaling records suggest Mr Johnstone may have ventured into the area.
North East Fife Chief Inspector Adrian Annandale told The Courier that police are growing increasingly concerned for his welfare.
Mr Johnstone was last seen around 9am on Saturday in Lunardi Place, which is close to the Tesco store in Cupar. He was reported missing by a member of his family.
He is described as 6ft, medium to stocky build with short thinning brown hair.
Inspector James Meek from Police Scotland said: “Gordon has not been seen or heard from for a number of days now, and concerns are growing for his safety the longer he remains missing.
“I would ask anyone who has spoken to or has seen Gordon, either on Saturday morning, or since that time, to contact police.
“Similarly I would appeal to Gordon to contact us directly so that we can reassure ourselves that he is safe and well.”
Anyone with information should contact Police Scotland on 101.