Two years? For aiming at an aircraft below... say 5000'? 15-20 years, for the reasons Andu gives in his post, should be more like it.
Manchester, with its "spotter's beer garden" and the road right alongside the taxiway, comes to mind as a potential problem airport if some group wanted to cause mayhem. These things, freely available to 14 year olds, look like being the near future weapon of choice for people with a political message to make or the mind/maturity of a 14 year old.
gimpgimp, I'm afraid my cynicism is such that I place company assurances like the one above up there alongside long time platitudes like "I'm from the Government and I'm here to help you", "Of course I'll still respect you in the morning" and "It's only a cold sore".