A Virgin Atlantic flight from London Heathrow to San Francisco was diverted following the eruption of Iceland's Bardarbunga volcano.
Flight V219 was rerouted as a "precautionary measure" the airline said.
Speaking to ITV News, a spokesman said: "Safety and security is always our top priority.
"All other Virgin Atlantic flights continue to operate as normal, but we are advising all customers to visit our website for the latest information.
"We continue to closely monitor the situation and we are in ongoing dialogue with all of the relevant authorities."
British Airways said it was closely observing the situation, the BBC reports.
The UK Civil Aviation Authority (CAA) has said that unless there is an actual eruption, there will be no impact on flights.
The Icelandic Met Office reported two magnitude 5 earthquakes throughout last night. It said these were the strongest measured since 1996.
"Probably, earthquakes near the Bardarbunga caldera are a consequence of adjustment to changes in pressure because of the flow of magma from under the caldera into the dyke which stretches to Dyngjujökull, more than 25 km away," a statement read.
The area around Bardarbunga, which is popular with tourists, has been evacuated.