In a post-9/11 world, there are few places where one can comfortably sit and watch airplanes come and go. A window seat on any jetliner flying at altitude is still the best vantage point if you know when and where to look.
Most people are unaware that commercial aircraft follow “airways” which are essentially roads in the sky. Like the ones on land, some are crowded and often intersect with other airways.
When the atmospheric conditions are right, you can find another plane by simply following the contrail. The best part of the day for this pastime is dusk, which can last a little longer in the air if you’re heading westbound.
A few days ago, while heading home from Baltimore, I got an extended dose of twilight and watched a few other planes that “slipped the surly bonds of earth.”