OK, did some research, and here's what i found. in the MM and BoED, all of the eladrins discuss what can be done in each form, except the tiny Coure eladrins. since the shiere had the same exact power in 2E as the coure, we just copied their entry.
now, if we need to expand the entry to spell that out anyway, i can tell you that except for the Shiradi (the only winged humanoid form) none of the eladrin could fly in humanoid form.