A Virgin Atlantic flight, VS3 from London Heathrow to New York, was forced to turn around after just over an hour on Monday as the Co-pilot had not completed their training and the captain was not a designated trainer.
Both crew members on the Airbus A330 were qualified to fly but the airline said that the Co-pilot had not completed their final assessment meaning they should only fly with a training captain.
As a result the flight was in breach of Virgins training protocols however no UK regulations were broken.
The Civil Aviation Authority said it was aware of the incident but stressed that both pilots were suitably qualified.
After returning to London Heathrow the Co-pilot was replaced and the flight continued on to New York.