Is a handbill a flyer or a flier?

Can Be Either Spelling, F-L-I-E-R Preferred

Definitions of flyer on the Web:

• circular: an advertisement (usually printed on a page or in a leaflet) intended for wide distribution; "he mailed the circular to all subscribers"
• flier: someone who travels by air
• aviator: someone who operates an aircraft

  Wordnetweb.princeton.edu/perl/webwn

Definitions of flier on the Web:

• someone who travels by air
• aviator: someone who operates an aircraft
• circular: an advertisement (usually printed on a page or in a leaflet) intended for wide distribution; "he mailed the circular to all subscribers"

  Wordnetweb.princeton.edu/perl/webwn

Both Words are used in English and are interchangeable.

Specifically, a handbill can be spelled flier or flyer, but the preferred spelling is flier for a handbill and any of the definitions above.