I live in a place that a lot of big airplanes fly over just after taking off from San Francisco International Airport. While I'm by no means perfect at it, I can often tell you what kind of jet is overhead, and even where it's going. There's a lot of people like me.
But there's also people who don't know anything about planes, and who can't tell the difference between very distinct behemoths like Boeing's 747 and Airbus' A380, let alone jets that on quick inspection look very similar, like Boeing's 737 and the Airbus A320. Or any of the dozens of other models ferrying passengers around at 30,000 feet.
That's why the Seattle PI has put together a handy primer on how to identify many of the most common planes making their way through our skies. From A320s and 737s to 747s and A380s, from Boeing 757s and 767s to Airbus A340s and others--each plane has distinguishing characteristics that the plane nerds recognize instantly, but which can be pretty quickly picked up by anyone who cares.
You might ask why those who aren't aviation nuts would care. Well, they might not. But if they want to impress the geek in their life, maybe they have an incentive to study the little differences. All I know is that not long after visiting the A380 factory in Toulouse, France last summer with my wife, she spotted one of the company's massive Beluga transport planes in the skies over France and pointed it out to me. She was very proud.