one   of the first I learned to spot was the Boeing 737.  It's the best selling commercial aircraft of all   time, it's everywhere. Once you know the trick,  it's incredibly easy to identify in the air.   It has no doors over the landing gear, if it's too  big to be a regional, it's a 737. You can see how   the gears swing out from the wheel shaped  cavities in the center of the fuselage.

aviation experts haddevised a solution to the problem of pilot interruption: the “sterile cockpit rule.”Instituted by the Federal Aviation Administration in 1981, the rule forbids pilotsfrom engaging in conversation unrelated to the immediate business of flyingwhen the plane is below ten thousand feet.