I usually hear planes flying overhead, although I don't really pay much attention to them. The only airplane I really notice is Aer Lingus' early flight from New York when it approaches Dublin Airport via the skies over north Wicklow around 5am. This isn't a daily occurrence nor does it always wake me, but there are times - on a Sunday morning, say - when I'd like to shoot the person who routed the huge plane low over my house.
For the most part airplane noises are just part the mix of sounds from cars and trucks and the occasional train that seems unimportant during the day. I'm surprised I even noticed the lack of planes, but I did. I also realized there were no jet engine trails in the sky either. The sun is shining and all the clouds above are natural.
I had thought that the quiet here was a result of the closure of all British airspace thanks to the ash from a volcano in Iceland, but I just read on RTE's web site that all flights in and out of Dublin Airport (& Shannon & Belfast) have also now been grounded.
In fact, the airspace over all of Ireland, Britain and the Scandinavian countries is now closed. Another example of nature's power.
I'm sure if I was traveling today I'd be at least somewhat annoyed, but I'm not. The lack of airplanes is simply a curiosity to me today and the source of a bit of peace and quiet.
UPDATE 1:50pm: Now it looks like this disruption could go on through tomorrow and possibly even into next week. I wouldn't have been so flippant about it if I'd known it would shut the airports down for more than a few hours.