On the fly means while something is happening, without preparation: we made up a new rule on the fly. It can praise flexibility or criticise haste. In tech, it means without stopping the program: the software resizes the image on the fly.
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change / decide / create something on the fly; an on-the-fly change
- When the screen stopped working, the speaker changed her explanation on the fly.
- We made up a new scoring rule on the fly because there were too many players.
- The software adjusts the image size on the fly while the video is playing.
What changed
First versionThe coach changed the plan on a fly when two players arrived late.
RevisionThe coach changed the plan on the fly when two players arrived late.
A quick decision feels like one event, so a seems right before fly. But the phrase is fixed with the: on the fly. Fly here means flight, not the insect, and the phrase has only one form.
On the go means busy and moving: I've been on the go all day. On the fly means improvising as you go: I changed the slides on the fly. In advance is the opposite: beforehand.
Your turn
The decision was made during the activity, without preparation: We decided on ___ fly.
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the — The phrase is fixed with the: on the fly. It isn't used with a.
Describe a time when a plan had to change while it was happening, and give the reason. Use on the fly.
The guide adapted the route on the fly when the bridge was closed.
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