Here are some possible interpretations:
* Incomplete phrase: It could be a shortened version of a longer phrase, such as "flies on the wall" (referring to an observer who is unnoticed).
* Slang: It might be a slang expression used in a specific region or community, with a meaning only understood by those familiar with it.
* Misheard phrase: It could be a mishearing of a similar phrase, like "flies on by" (meaning something happens quickly or passes by).
To understand the meaning of "flies on," you need more context.
For example:
* "The time just flies on..." This likely means time is passing quickly.
* "He was just standing there, flies on..." This could be referring to someone who is unmoving, perhaps bored or inactive.
If you can provide more context about where you heard the phrase, it might be possible to decipher its intended meaning.