What happened
On a flight departing Málaga, Spain, at 19:30 UTC bound for London-Heathrow, an Iberia aircraft was navigating through misty conditions and light drizzle. During the descent toward the United Kingdom, air traffic control issued several altitude instructions. After passing certain waypoints, the crew was cleared to descend to FL210, then later to FL110, and eventually to FL60. While passing Fawley, the crew acknowledged a clearance to FL60, noting they were currently at FL145. Shortly after being cleared to fly direct to Epsom, the aircraft entered a continuous descent.
The aircraft struck trees on the southern slope of Blackdown Hill, roughly 48 km south-southwest of Heathrow Airport. Following the initial impact, the wreckage traveled across a meadow where it killed 65 sheep. The debris field continued through a hedge, causing the destruction of a garage and damage to the roof of Upper Blackdown House as the aircraft disintegrated. There were 37 fatalities among the occupants, with no survivors.
Findings
Investigators were unable to determine the specific reason why the aircraft continued its descent below the assigned altitude. The investigation examined whether the crew had misread the three-pointer altimeters, which feature cross-hatching in the 10,000ft window. While a misreading of 6,000ft as 16,000ft was considered possible due to the movement of the pointers during a long descent, the crew's report of passing FL145 suggested they were aware of their actual altitude at that time. Although investigators noted the possibility of a mental loss of sequence regarding altitude and time, no definitive cause for the uncontrolled descent could be established.