Hundreds of thousands of travellers are taking to Europe's skies after nearly seven days of flight cancellations and closed skies caused by the eruption of an Icelandic volcano.
Airlines say the forced groundings cost them $1.7bn and say flights could have resumed earlier.
But a study by Swiss scientists has found levels of airborne volcanic ash warranted the shutdown.
Al Jazeera's Nadim Baba reports on the financial costs of the shutdown.
Source: Al Jazeera