#1 – fly by
If you say that time is flying by, it means that it feels like the time is passing very quickly.
How can it be September already? This summer just flew by!
We also have the expression is time flies when you’re having fun – meaning that time seems to pass quickly when you’re enjoying yourself.
#2 – 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.
Right before my presentation, I was informed that I only had 10 minutes to speak instead of 30 – so I had to shorten the presentation on the fly. (=shorten the presentation while giving it)
#3 – 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).
We don’t really have a marketing plan – we’ve just been flying by the seat of our pants.
#4 – sparks fly
If sparks fly between two people, it means they are having an angry and intense argument.
Sparks fly every time she has to interact with her ex-husband.
#5 – 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).
The scientist’s radical theories fly in the face of everything we know about physics.
#6 – fly into a rage / fly off the handle
Both of these idioms mean to get angry very quickly, to lose your temper.
He completely flew off the handle when I suggested that he was lying.
#7 – It’ll never fly
If you say that something will never fly, you are saying it will not succeed.
You can suggest a change to the company policy… but I’m warning you, it’ll never fly.
#8 – When pigs fly! / Pigs might fly.
This idiom is a funny way to say you very much doubt that something will happen… you think it is almost impossible for it to happen.
“My favorite team is definitely gonna win the championship this year!”
“Yeah… and pigs might fly! That team is the worst in the league.”
#9 – 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.
Sarah passed her driver’s test with flying colors – the instructor said she was the best in the class.
#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.
I bought this watch from some fly-by-night shop, and it broke within three weeks.