All routine offshore helicopter flights in much of Europe remain suspended following last week's eruption of Iceland's Eyjafjallajokull volcano, which resulted in a dangerous ash cloud.
In a statement, Oil & Gas UK said operators are using boats to perform crew changes and some operators have started scaling back on non-essential activities, however, search-and-rescue aircraft and air ambulances in the UK remain operational.
Helicopter flights from UK airports into the UK Continental Shelf were suspended last week following an airspace restriction due to the cloud of volcanic ash, which experts say poses a significant risk to plane engines.
Helicopter flights to the Conoco-Phillips-operated Ekofisk platform in the North Sea have also been suspended due to the risk of volcanic ash, according to Avinor, Norway's airport authority.
Production at Ekofisk, which produces most of Norway's oil, has not been affected.
Some domestic flights are taking off in the UK as airports begin to reopen after five days without flights following the volcano's eruption.