To fly by the seat of your pants (or "trousers," if you're from the UK), means to do something based on your own instinct, rather than following outside help or a pre-set plan.
The expression comes from aviation and has been around since the 1930s, if not a little earlier. (It's safe to say it's no earlier than 1903!) In the early years of flight, planes had few pieces of equipment to guide them on their course, so pilots had to rely on their own judgement and perception. Those pilots were said to fly by the "seat of their pants."
Since then, it has come to mean someone who does ANY sort of endeavor relying on his or her judgement. (Example: Because the first-year teacher had no experience with a science lab, he tended to create his lesson plans by the seat of his pants.)
Hope this helps!
The expression comes from aviation and has been around since the 1930s, if not a little earlier. (It's safe to say it's no earlier than 1903!) In the early years of flight, planes had few pieces of equipment to guide them on their course, so pilots had to rely on their own judgement and perception. Those pilots were said to fly by the "seat of their pants."
Since then, it has come to mean someone who does ANY sort of endeavor relying on his or her judgement. (Example: Because the first-year teacher had no experience with a science lab, he tended to create his lesson plans by the seat of his pants.)
Hope this helps!