on the fly meaning

• Adverb: on the fly
  1. On the run or in a hurry
     "she wrote those letters on the fly"

  Encyclopedia: On the fly

• 
  [American slang]
  [done] while something or someone is operating or moving.
    I'll try to capture the data on the f ly.
     Please try to buy some aspirin somewhere on the f ly today.

• fly:    Verb: fly (flew,fl ...
• fly at:    fly at sb to sudde ...
• fly by:    fly by if time fli ...

Examples

1. the bird caught a bug on the fly.
2. do you run through each day on the fly
3. insert printk s into the linux kernel on the fly
4. do you run through each day on the fly
5. study on the fly ash geopolymer material and its property