Air accident investigators have launched an inquiry after a helicopter landed on the wrong North Sea platform this week.
On Monday, a Bristow helicopter touched down on the wrong installation at the Apache-operated Forties field.
It is understood the helicopter landed on the Charlie platform, when it was intended to land on the Delta.
Offshore platforms expecting a flight to arrive are made to stop activities which could put the aircraft at risk.
This includes crane operations and venting of flammable gas, which can be dangerous to fly through, and making sure helidecks are properly manned.
The Air Accident Investigation Branch (AAIB) has confirmed the incident has been reported and it has launched an investigation.
Bristow said there was no disruption to operations and the passengers were quickly flown to the right installation.
A spokesman said: “We can confirm an aircraft landed on an incorrect platform on Monday this week.
“There was no impact to routine operations as a result of the error, and passengers were flown to the correct installation without further delay.”
Bristow did not explain what caused the mistake.
Jake Molloy, regional organiser of the RMT Union said: “This is astonishing.
“I was of the understanding that systems and procedures were put in place some time ago to ensure this kind of event couldn’t happen, again.
“It seems we introduce systems to address failures that have the potential for a major incident, then after a period of time those systems are forgotten.
“You have to question how learnings from previous events of this nature are lost.”
An Air Accidents Investigation Branch spokesman said: “The incident was reported to us and we are investigating.”
The Forties field lies around 140miles north-east of Aberdeen.
John Boland, regional officer at the Unite union said: “It’s very concerning. These pilots are very experienced and you would expect that they are landing on the correct platform.
“The concern is if the platform wasn’t actually ready for the helicopter landing, and there were operations going on, that could have been a much more serious situation.”