adamnaylor #120,
You're far from alone in using 5mW class pointers - #41 does, and my #63 also describes uses of potentially dangerous 10-100W yellow lasers by professional astronomers to measure and correct their images for atmospheric turbulence (certified and regulated by the FAA in the US).
If you can see an aircraft's strobes, then the crew could see your laser. I think we should leave it to you to use your judgement and turn the laser off or away if and when you see an aircraft. Pointers are used to point for a crowd. That means witnesses, and so while you should keep a lookout for aircraft, you're not going to be in trouble for legitimate use.
Human spotters with dead-man's handle kill switches are the safety system for telescopes' 10-100W sounding lasers: if strobes are seen within 25 degrees of the beam, then the light is shuttered immediately: see
http://www2.keck.hawaii.edu/optics/l...cs/kaon361.pdf for one set of protocols.
Added thread link, Oct 30th: best discussion of the appearance and risks I've seen so far in
http://www.pprune.org/rotorheads/320314-l-ser-searchlight-attacks-aircraft-incl-prison-sentences-offenders.html#post3704281.
Credit to the site for tying it in at the bottom of this thread.
I assume the blinding effect of scattering from scratches on the windows is less of an issue for airliners with glass cockpit windows than for the police helicopters described on the linked thread.