On the fly is an idiom that seems to have originated in the United States. We will examine the meaning of the idiom on the fly, where it may have come from, and some examples of its use in sentences.
On the fly means to do something spontaneously, to solve problems as they come up, to adapt to an ever-changing environment. To do something on the fly means to do something without thought, one simply reacts to the situation as problems are presented. The expression on the fly most probably originated with American baseball and came into use in the mid-1800s. A fly in American baseball is a ball that is hit by the batter into the air, without the ball touching the ground.
Whether the effects are obvious or more subtle, the coronavirus pandemic has made an impact on every facet of life, business and culture, forcing institutions to adapt on the fly. (The Bulletin)
Mobile test sites make adjustments on the fly (The Examiner Enterprise)
Illinois adjusts on the fly to meet medical supply needs in a coronavirus ‘Wild West’ (The Chicago Sun Times)