Doctor Margaret Ann Rous, 37, and her husband, engineer David Rous, 28, were killed when their Piper Cherokee plane went down near Oban, Argyll and Bute, on April 4 last year.
The couple, who lived in Newport-on-Tay in Fife, were heading from Dundee for an Easter weekend visit to relatives on the Hebridean isle of Tiree at the time.
A team from the Air Accidents Investigation Branch (AAIB) was sent to the crash site and have published a report into the incident.
They found the aircraft struck the western slope of the mountain Beinn nan Lus in a “steep nose-down attitude”, describing the impact as severe.
But investigators said no “specific” cause for the accident could be identified.
The AAIB report said Mr Rous, the pilot, and his wife died as a result of “multiple injuries sustained in a non-survivable accident”.
Investigators concluded: “No specific cause for the accident could be identified but the descent in instrument meteorological conditions (IMC) with extreme aircraft attitudes suggests that the pilot was experiencing some form of spatial disorientation; the recorded data and impact parameters suggest that the accident occurred following a loss of control, possibly in cloud.
“Whether this was due to an attempted turn back manoeuvre or simply loss of control in IMC is not known.
“In addition, the meteorological conditions were conducive to airframe icing, which had the potential to degrade the aerodynamic characteristics of the aircraft and thus may have been a factor in this accident.”
A loss of radar contact with the aircraft on the day of the accident had prompted a multi-emergency response involving the police, ambulance service and the coastguard.
Searchers discovered the wreckage that evening.