Of course creating these life-like characters almost always involve drawing on the characteristics of real people. Clearly you can't create a character that's an exact copy of someone you know. (Unless you're writing their biography.)
I recently found myself in the (un)fortunate position of arriving at the airport to discover my flight had been delayed. Most people would get all in a huff about it. As a writer, it's the perfect opportunity for me to observe people's behaviour and study their mannerisms without influence. Being stuck at an airport for two hours is a great way to practice character development and building back story.