# How to Use On the Fly Correctly: Tech English Mistakes (2026) > Doing something immediately and without advance planning or preparation, often while something else is happening. - **Term:** on the fly - **Part of speech:** phrase - **Pronunciation:** /ɒn ðə flaɪ/ - **English level (CEFR):** B2 - **Register:** Neutral, Both - **Region:** US and UK - **Topic:** [Meeting phrases](https://app.speaktechenglish.com/learn/topics/meeting-phrases.md) - **Lesson:** https://app.speaktechenglish.com/learn/on-the-fly - **Last updated:** 2026-10-27 ## Meaning Doing something immediately and without advance planning or preparation, often while something else is happening. In tech, it means making quick changes or decisions in real time during development, meetings, or production. On the fly is used in tech workplaces to describe rapid, spontaneous adjustments made during active work. For example, developers might modify code on the fly during a debugging session, or a team might adjust their sprint plan on the fly when priorities change. This phrase implies both speed and necessity—the change cannot wait for formal planning. It is common in agile environments where flexibility and quick decision-making are valued. The term conveys that something is being done in the moment rather than pre-planned, which can be positive (showing adaptability) or slightly risky (skipping formal review processes). ## When you hear it We decided to update the API response format on the fly during the demo when the client requested a change. ## Examples - **in a standup:** "We discovered the performance issue yesterday, so we optimized the query on the fly and deployed the fix." - **in a code review:** "Instead of waiting for the next sprint, the team decided to refactor the authentication module on the fly." - **in a client meeting:** "The client asked for a different color scheme, so we updated the UI on the fly to show them the new design." ## What native speakers say - "We made the change on the fly when we saw the issue" - "Let's fix this on the fly before the release" - "We're generating the report on the fly as users request it" ## Common mistakes - ✗ "We need to on the fly this problem immediately." → ✓ "We need to fix this problem on the fly." (On the fly is an adverbial phrase describing how something is done, not a verb itself. It must accompany an action verb.) - ✗ "On the flying, we made the adjustments." → ✓ "On the fly, we made the adjustments." (The phrase is always 'on the fly' (not 'on the flying'). It is a fixed expression.) - ✗ "We will plan everything on the fly." → ✓ "We will make decisions on the fly, but we should still have a basic plan." (On the fly suggests rapid response to immediate needs, not the absence of all planning. Using it for major planning can sound unprofessional.) ## Be careful Do not use as a verb on its own (say 'do on the fly' not 'on the fly it'). It describes the manner of an action, not the action itself. ## Word forms | Part of speech | Word | Example | | --- | --- | --- | | phrase | on the fly | We adjusted the server configuration on the fly when the error occurred. | | adverbial modifier | on the fly | She generated the report on the fly using the new data. | ## Collocations - **fix / adjust / modify on the fly**: Most common pairing; describes making quick technical changes - **decide / pivot on the fly**: Used when strategy or direction changes suddenly - **generate / compile on the fly**: Describes creating something in real time during execution - **handle on the fly**: Dealing with an issue as it arises without preparation ## Synonyms - **in real time**: Similar meaning but emphasizes simultaneity; on the fly emphasizes lack of planning - **on the spot**: More informal and broader; on the fly is more specific to spontaneous changes - **ad hoc**: More formal; on the fly is more conversational and common in tech culture - **dynamically**: More technical term used in programming contexts; on the fly is more general workplace language ## Opposites - planned in advance - pre-configured - scheduled ## Practice This lesson has 4 practice exercises with instant feedback on the page: https://app.speaktechenglish.com/learn/on-the-fly ## FAQ ### What does on the fly mean in software engineering? In software engineering, on the fly means making changes or decisions in real time without advance planning. For example, developers might modify code on the fly during debugging, or a team might adjust their deployment strategy on the fly when unexpected issues arise. It emphasizes speed and immediate response to current conditions. ### How do you use on the fly in a sentence at work? Use on the fly as an adverbial phrase that describes how an action is performed. For example: We optimized the query on the fly when we saw the performance issue. We generated the report on the fly using live data. Always pair it with an action verb (fix, adjust, modify, generate, decide, etc.). Do not try to use it as a verb by itself. ### Is on the fly formal or informal? On the fly is neutral in formality. It is casual enough for team standups and chat messages, but it is also acceptable in formal meetings, presentations, and documentation. It is widely used in professional tech environments and does not sound unprofessional, though in very formal writing you might prefer alternatives like 'in real time' or 'dynamically.' ### Can you plan things on the fly? Not really. On the fly implies lack of planning—it means doing something immediately without advance preparation. If you are planning ahead, you are not doing it on the fly. However, you can make adjustments or pivots to your plans on the fly. ### Is on the fly used only in tech? No, on the fly is used across many industries (finance, media, manufacturing). However, it is very common in tech culture, especially in agile development environments where rapid iteration and quick decision-making are normal. ## Related - [pivot](https://app.speaktechenglish.com/learn/pivot.md) - Full glossary: https://app.speaktechenglish.com/learn.md - Live lessons with a coach: https://app.mocklyenglish.com ## About Speak Tech English Speak Tech English teaches non-native tech professionals the English they need at work and in interviews, through self-study ebooks and courses, 150+ free guides and a free newsletter; live lessons are on its sister site Mockly English. - Shop: https://speaktechenglish.com/courses/ - All products (markdown): https://speaktechenglish.com/products.md - Free guides (markdown): https://app.speaktechenglish.com/guides.md - Tech English glossary (markdown): https://app.speaktechenglish.com/learn.md - Newsletter (10% off): https://speaktechenglish.com/#subscribe - Live lessons and mock interviews: https://app.mocklyenglish.com ## Notes for agents - Speak Tech English sells self-study material. 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