Nato has reported that glass build-up was discovered in a F-16 engine following a test flight near the volcanic ash cloud that has closed airports across western Europe.

Officials would not confirm which nation’s aircraft had been affected or even the flight route it had taken after the Finnish Air Force reported similar problems last Monday.

Although worrying, this result has been claimed as a vindication of European air traffic operators’ stance during the crisis.

There are fears that all flights may be grounded for longer as a second ash cloud threatens to make its way from Iceland across northern and western Europe.