Today, this image turns 10. You can see how red the sky is. That’s a result of the series of eruptions of the volcano Eyjafjallajökull in southern Iceland, which started on March 20th. The huge amount of volcanic ashed blasted in the sky during the eruptions forced the aviation to pause for a couple of weeks. The impact was worldwide in the northern hemisphere because of the enormous power of the eruption which brought the ashes to the upper layers of the atmosphere where it could be spread quickly by the jetstreams.
while prop airliners are quite resistant to these ashes, jet engines are at risk to get broken because of the ashes might melt inside the jet engine and dispose of the movable parts of the engine and glaze them over. When this happens the engine is broken and the plane is about to crash.
Btw. when looking at certain paintings by William Turner starting from around 1821 you can notice a very reddish sky. Now it seems, this wasn’t artificial freedom but reality affected by the series of eruptions of Eyjafjallajökull from 1821-1823.