This is worth a read..
"The Effects of Laser illumination on Operational and Visual Performance of Pilots During Final Approach"
http://www.faa.gov/library/reports/m...media/0409.pdf
It says that "illumination of flight crewmembers with laser radiation > 0.5uW/cm^2 is unacceptable"
Someone check my sums but....
A 500mW output laser spread over a 1 meter diameter spot would be around 64uW/cm^2. Thats 128 times the acceptable level.
Spread over a 1.5m diameter spot it's still around 28uW/cm^2 or 56 times the acceptable level.
If the spot diameter is 3m (see previous posts) the max acceptable power of the laser works out at just 35mW.
So if those spot diameters are achievable at the required range (see earlier posts) it would appear easy for the recommended max exposure of 0.5uW/Cm^2 to be exceeded.
I've ignored absorbtion by the air.