Welcome to Thinking in English. Today I want to introduce some common English idioms, proverbs, and expressions using the word “fly”. Check out my blog to find a full transcript with all of the phrases I mention included. thinkinginenglish.blog or the link is in the description. And follow me on Instagram!

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This episode of Thinking in English will explore a variety of expressions and idioms that use a version of the verb ‘to fly.’ ‘Flying,’ as in traveling through the air, has fascinated people for centuries. Therefore, it is natural for English vocabulary to incorporate and embrace idioms based on the word fly. All of the following phrases are used in contemporary English, so why not try to use one in your next conversation?  

Birds of a feather fly together

Let’s start with a classic English proverb – Birds of a feather fly together! This idiom suggests that people who have similar ideas, characteristics, or interests become good friends or get along well with each other. You may hear this idiom shortened to simply Birds of a feather or slightly modified to birds of a feather flock together. The idea is that similar people associate well with each other. For example, “I knew Emily and Jessica would be great friends – birds of a feather fly together, after all.”

Fly at (someone or something)

Have you ever been so furious that you suddenly and violently attacked or hit someone? Probably not. But if you have, we could say that you flew at someone. To fly at someone or something means to abruptly, suddenly, and violently attack or strike someone or something. A person can fly at someone else: for instance “my roommate flew at me in anger and grabbed his diary out of my hand.” Or an animal can fly at something or someone: for example “the large dogs flew at each other.”

Fly into a rage/temper

To fly at is not the only idiom in this list describing an angry situation. If you fly into a rage or fly into a temper, you become uncontrollably angry, suddenly enraged, and lose control of your temper. The key point is the sudden and perhaps unexpected change from normal into angry. Something shocking normally causes this to happen! For example, “His father flew into a rage when he failed his High School exams!” or “The employees were terrified that their boss would fly into a temper when he saw their report!”

Fly beneath (the/someone’s) radar

The next idiom is to fly beneath the radar or fly beneath someone’s radar! Radar is a system used to detect the location and direction of aircraft, ships and objects by using radio waves. If something flies beneath the radar it is undetectable! So, the idiom to fly beneath the radar means to go without being noticed, detected, or addressed. It could be a person or an issue. For example, “The band is really good but their new album is flying beneath the radar.” Another example is “The problem of homelessness always flies beneath the government’s radar.”

Fly in the face of

If you fly in the face of something or someone it means that you are challenging something or someone; acting in conflict or opposition to something else. You’ll often hear it in conjunction with the word everything. A few years ago I had to design a project for some students, but at the last moment my boss changed the theme of my project which flew in the face of all my hard work! Let me give you some more examples! First,  “I can’t believe you said something so awful. It flies in the face of everything we stand for!” Second, “Her controversial new theory flies in the face of everything we know about modern physics.”

Fly off the shelves

Sometimes, when products are really popular customers will buy them almost as soon as a shop puts them on the store shelves. Well, we have an idiom to describe this situation: to fly off the shelves! Fly off the shelves means to sell incredibly quickly, as though the items in question cannot be kept on store shelves. As soon as they are put on the shelves, they are grabbed by customers. I used to work at a supermarket in the evenings, and during the Christmas period I would put Turkey or ham out on the shop floor, and after only two or three minutes they would have been bought already: they flew off the shelves. Here are some example sentences. “The new PlayStation has been flying off the shelves – stores are selling out in only a few minutes!” “Even though that newspaper is low quality, it always flies off the shelves because people love reading about celebrities.”

When pigs fly

We use the idiom when pigs fly to show scepticism, cynicism, or doubt over a hypothetical situation or an impossible suggestion. Pigs cannot fly; and are never going to be able to fly. So, if you say something will happen when pigs fly it will probably never happen. If your boss is a very stingy or tight person (meaning he doesn’t like to spend money) you could say “I’m sure our boss will treat everyone to dinner – when pigs fly!” Or “Sarah said she will go on a date with Jim – when pigs fly!”


When I thought of the initial idea of this episode, I was just thinking of idioms using the verb “to fly.” But I quickly remembered that we also use quite a few idioms using the noun “fly.” Flies are small insects that can fly using wings (and many people consider them to be annoying). So, as a bonus, here are three commonly used idioms based on the insect!

A fly on the wall

Flies are so small, and so common, that often we don’t notice when they are in our houses and rooms. If you would like to be like a fly on the wall, you would like to secretly hear what is said in the room or see what happens. You would be able to observe something closely but invisible without interfering in the situation: just like a fly on the wall. We use this when we want to know what is happening in a private situation. For example, “I would love to be a fly on the wall in Dave’s house when he discovers that his wife lost her wedding ring.” Or “I’d love to be a fly on the wall of the President’s office during a crisis meeting!”

A fly in the ointment

Imagine if you bought a medication or ointment from the drug store, only to discover a fly inside – you would be horrified! I think you’d probably no longer be confident in the medication. A fly in the ointment  is a flaw or imperfection that detracts from something positive. The one negative thing which stops a good thing from being perfect. For example, “The only fly in the ointment in an otherwise perfect wedding day was the fact that the bride tripped when walking down the aisle.”

Wouldn’t hurt a fly

Flies are quite annoying insects and many people try to kill them when they get stuck inside the house. If you wouldn’t hurt a fly you must be a very gentle person. The idiom wouldn’t hurt a fly is used to say someone would harm nothing or no one. We say it about a person who is particularly gentle, shy, diffident, or timid by nature. It is also said to defend people who are accused of committing a crime! For example, “My brother is a very sweet, warm-hearted man who wouldn’t hurt a fly. How can you suspect him of committing this crime?”

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By Tom Wilkinson

Host and founder of Thinking in English, Tom is committed to providing quality and interesting content to all English learners. Previously a research student at a top Japanese university and with a background in English teaching, political research, and Asian languages, Tom is now working fulltime on bettering Thinking in English!

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