Flyer-Flier | Commonly Confused Words

Flyer

/ˈflaɪə/

A small paper advertisement or notice used for promotion

A small leaflet or paper advertisement distributed to attract attention and inform about something

Flyer and flier can often be used interchangeably, but flyer is the more commonly preferred spelling in most English-speaking countries.
Both words are used to refer to a handbill or leaflet.
Flier is chiefly used in the United States, while flyer is preferred in British English.
In aviation, flyer is often used to describe a person who flies, but flier is also accepted.
When in doubt, you can use flyer as it's more universally accepted.