Ian Stirling, a former director with building company Allanwater Developments, was flying solo from his home on the Isle of Man to Blackpool when the aircraft disappeared from radar after encountering stormy weather in December last year.

The 73-year-old had been due to land at Blackpool Airport, but a major search and rescue operation was launched after the plane failed to arrive.

The Rockwell Commander plane was later discovered buried deep in the seabed, but Mr Stirling’s body could not be recovered.

Mr Stirling served as a director with the Bridge-of-Allan based Allanwater Developments before his son David took over the multi-million-pound business.

Now, according to The Herald, his published will has now revealed he had an estate totalling £6,558,526 at the time of his death.

He ordered it should be passed to his widow Elizabeth. The couple have three sons, David, Mark and Jamie.

Legal papers show his fortune was made up of properties worth £2.25m shares in Allanwater Developments valued at £3.2m and personal effects totalling £150,000. Mr Stirling also had about £900,000 of other investments.

A memorial service was held for him in Dunblane Cathedral in January and was attended by family and friends.

At the time of the accident, a spokesman for Mr Stirling’s family said Ian was “an experienced pilot who had flown this route many times”.

An inquest later recorded a verdict of accidental death and coroner Alan Wilson said the businessman’s family had taken the decision that they would prefer his remains were left in the downed plane.

Mr Wilson said it was unusual to hold an inquest without a body, and could not offer a cause of death, but said he was satisfied Glasgow-born Mr Stirling remained inside the aircraft.

The inquest came soon after an Air Accidents Investigation Branch (AAIB) report said the plane’s cockpit was likely breached when the plane crashed at a dangerously low speed and acute angle.