It is a real threat. Enough of a threat for the FAA to mail out a Pilot Safety Notice (Linked PDF). Let me explain why, as a counter to each of your points in the original question:
- First of all, planes bank and turn, so they aren't always perpendicular to the ground. Also, the Plexiglas material that aircraft windshields are made of further scatter and intensifies the dazzle effect on a pilot that happens to be sitting right up on the window. So you don't need to shine it directly at the pilot, just the cockpit.
- The greatest danger is not for high flying aircraft, but rather while aircraft are in critical phases of flight. That is not to say that you can't have an effect on higher flying aircraft. There is a property of lasers called divergence that will allow you to cover a fair area of the sky. Although, then the inverse square law takes over, so the power getting to a pilot at those distance normally wouldn't be a concern for most, although it may screw up night vision.
- You greatly overestimate the amount of time an aircraft is on autopilot. Generally, below 10,000 feet is where most professional pilots will take over from the autopilot in order to warm up for the landing phase. (This is a TTP for pilots.) It actually tunes you in for greater Situational Awareness (SA), and will have you looking out of the cockpit more than when on autopilot. Thus making you more susceptible to a laser dazzling effect.
- It only takes a small amount of light to screw up your vision for landing phases. This is especially dangerous during night operations. It is also intensified again by the scattering that you get from the Plexiglas as I mentioned in item 1. Add to that that green light is the most "dazzling" wavelength.
Specific effects as listed here are:
Distraction and Startle: This occurs when an unexpected laser (or other bright light) can distract a pilot during a night time take-off or approach/landing.
Glare and Disruption: This occurs as the intensity of the laser light increases such that it starts to interfere with vision; night vision starts to deteriorate.
Temporary Flash blindness: This effect is similar to that experienced when looking at a bright camera flash. There is no injury, but a portion of the visual field is temporarily knocked out. Sometimes there are ‘afterimages’.
And you are lucky that the old guy didn't call the Military Police on you. They have a procedure for reporting these incidents (called a SAFIRE). It has even happened with civilians.
New law to combat louts dazzling pilots over Birmingham with lasers pens (that's Birmingham in the UK).
PILOTS flying over the skies of Birmingham are facing a greater threat of being dazzled by a laser pen than almost anywhere else in the country, it has emerged.
The region is third in a ‘league of shame’ of hotspots for the crime according to a report by the UK Civil Aviation Authority.
Now they have introduced a new law to target the reckless offenders putting the lives of those in airliners and helicopters at risk.
Man arrested for trying to dazzle pilots with laser
(Reuters) - A man appeared in court on Tuesday accused of trying to dazzle pilots with a laser beam as they were landing at France's second-busiest airport Paris Orly, aviation authorities said.
"Several pilots complained and the man was arrested near the runway," a spokesman for the civil aviation authority said.
Aussie laser-pointer dazzle attacks on airliners: Bad
Australian politicians are demanding restrictions on the ownership of laser pointers in the land down under. The banning calls follow a series of widely-reported incidents in which individuals on the ground have attempted to dazzle pilots of commercial aircraft making approaches to landing.
A particularly troublesome dazzling attack took place last Friday, involving at least four comparatively-powerful green laser pointers in the Bexley area of Sydney. Six passenger flights were affected, with air-traffic controllers having to re-route the planes.
"The use of these laser pointers against aeroplanes is unbelievably stupid and cannot be tolerated," Australian Home Affairs Minister Bob Debus told the Sydney Morning Herald.