Pilots of a passenger plane were 'unaware' the aircraft plummeted by more than 1000 feet in less than a minute above Aberdeen International Airport, an investigation revealed. 

The Scottish airport has now updated procedures and further guidance has been issued to pilots by Boeing after the "serious" incident took place on September 11, 2021. 

Flying from Palma to Aberdeen, the Boeing 737 had 67 passengers and six crew members on board when the incident occurred during a go-around - an aborted landing that is on final approach. 

The manoeuvre can be vital when there is an obstacle on the runway or poor environmental conditions.

In the case of the flight on Septermber 11, the pilots were told they would need to abort landing to make way for a search and rescue helicopter and return to 3000ft above sea level. 

As it approached that height, the plane began dropping suddenly and reached just 1565 ft above sea level in just 57 seconds. 

It is thought they began correcting the rapid descent at the same time as the control tower noticed the issue. 

An alert system which is supported to warn of an aircraft with a rapid rate of descent failed to recognise the descent rate exceeded 2,500 ft/min for a total of approximately nine seconds.

The investigation by the Air Accident Investigation Branch (AAIB) said it was likely the crew allowed the aircraft to descend unnoticed after the go-around heightened the burden on the pilots. 

The report adds: "The crew were assigned several heading changes both before and during the aircraft descent.

"These instructions placed an additional burden on a crew that was already working hard."

In addition to a high pressure situation, the pandemic also impacted the flight staff as both "pilots had experienced significant periods away from flying the aircraft type". 

A drop in the number of flights being operated during the pandmeic also meant the pilots would be less likely to have recently performed a go-around. 

"With a go-around rate around three per 1,000 flights in the UK, the average crew from the operator might have expected to experience one a year when flying at the pre-pandemic rate," the report reads.

The commander had flown ten flights during the previous month, while for his co-pilot this was only his fourth flight in nearly 11 months, having completed two training flights seven days before the day of this incident.

As a result of the incident, Aberdeen’s air traffic control changed its procedures for aircrafts being broken off from the approach.

Meanwhile, Boeing updated guidance to pilots about the behaviour of the Autopilot and Flight Director System (AFDS) and autothrottle during go-arounds.

The aircraft operator informed all its pilots about the event and included extensive go-around training in its training cycle. 

It also reviewed how recently all pilots had flown and introduced  additional restrictions to manage pilots through periods of reduced flying.