This line of code alone:
Code:
<span style="font-family: 'Futura Light'; font-weight: normal; font-size: 1em; line-height: 1.083;"><br /></span>
Won't produce the FlightCrew error you indicated (even if there are no font files included in the epub).
The references you probably need to remove are the @font-face declarations in the CSS (in the head of the page or in an external stylesheet). Specifically: any "src: url(...);" statements that are pointing to non-existent font files.
You've only included the error message from FlightCrew. The first column in the error will indicate the resource/file that doesn't exist (but is being referenced somewhere) in your epub. If that first column isn't a font file "OEBPS/Fonts/something.ttf/otf". Then your problem is something else.