 Ten English idioms with the word fly from espressoenglish.net. Number one, fly by. If you say that time is flying by, it means that it feels like the time is passing very quickly. For example, how can it be September already? This summer just flew by. We also have the expression, time flies when you're having fun, meaning that time seems to pass quickly when you're enjoying yourself. Number two, on the fly. Doing something on the fly means without previous planning. You are doing it at the same time as your action is in progress. For example, right before my presentation, I was informed that I only had ten minutes to speak instead of thirty, so I had to shorten the presentation on the fly. This means you had to shorten the presentation while giving it. Number three, fly by the seat of your pants. If you are flying by the seat of your pants, it means that you are operating with luck and intuition and without previous planning or preparation. For example, we don't really have a marketing plan, we've just been flying by the seat of our pants. Number four, sparks fly. If sparks fly between two people, it means they are having an angry and intense argument. For example, sparks fly every time she has to interact with her ex-husband. Number five, fly in the face of. When a fact, idea, or statement challenges or goes against some established fact, we say it flies in the face of the fact. For example, the scientists' radical theories fly in the face of everything we know about physics. Number six, fly into a rage or fly off the handle. Both these expressions mean to get angry very quickly to lose your temper. For example, he completely flew off the handle when I suggested that he was lying. Number seven, it will never fly. If you say something will never fly, you are saying it will not succeed. For example, you can suggest a change to the company policy, but I'm warning you, it will never fly. Number eight, when pigs fly, or pigs might fly. This is a funny way to say you very much doubt that something will happen. You think it is almost impossible for it to happen, like a pig flying. For example, if you and your friend root for opposite sports teams, he might say, my favorite team is definitely going to win the championship this year. If you very much doubt that, you could say, yeah, and pigs might fly. That team is the worst in the league. Number nine, pass with flying colors. If you pass a test or evaluation or complete a difficult task with flying colors, it means you passed it successfully and excellently. For example, Sarah passed her driver's test with flying colors. The instructor said she was the best in the class. Number 10, fly by night. Describing a person or company as fly by night means they are unreliable and irresponsible, and their work is probably not of good quality. For example, I bought this watch from some fly by night shop, and it broke within three weeks. To learn 260 common idioms used in everyday spoken English, take the English Idioms course available at espressoenglish.net. You'll discover English idioms in context and practice using them with exercises. Visit espressoenglish.net to take the English Idioms course.