In FontCreator 14，use Export Font–> Export as Desktop Font(ttf/otf)，only can Export TTF fonts，can’t Export OTF fonts.
How to Export otf Fonts in FontCreator 14?
Please see this earlier thread.
The font extension does not matter, but I would also prefer it if *.otf were used for TrueType outlines as well as for CFF Postscript outlines. Renaming the exported fonts is one step that I don’t want.