Ryanair said its 90-minute flight at 41, 000ft showed there was "no visible volcanic ash cloud or evidence of ash on the airframe, wings or engines".

BBC: NI flights cancelled as ash cloud approaches

In September, the NTSB recommended the FAA require large planes and other aircraft on which the wingtips are not easily visible from the cockpit to have cameras or other devices to monitor the wings.

CNN: STORY HIGHLIGHTS

In September the National Transportation Safety Board recommended the Federal Aviation Administration require large planes and other aircraft on which the wingtips are not easily visible from the cockpit to have cameras or other devices to monitor the wings.

CNN: Spirit Airlines plane hits parked jet