Laser attacks on aircraft started some years ago when laser pointers became readily available and have now escalated such that 2,300 events were recorded on the CAA’s Mandatory Occurrence Reporting database for 2011. As the CAA is not always informed of an attack the actual number of attacks may significantly exceed this figure. The vast majority of attacks take place when aircraft are over or near large centres of population and occur both in the UK and overseas. In addition, ATC towers have also been targeted by lasers. 

Source:  http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=4967