Thx everyone.
Funny, I too only have a middle initial (I know...right???)...LOL...but for the person who asked, I think the key is that your documents should match your passport. In my case, my passport has only my middle initial, so I don't think any further proof is necessary that there's no middle name...as long as tickets match.
I'm just annoyed b/c Air China didn't even give me the option.
UPDATE: I called TSA & asked them & they said that b/c not all the airlines are "on board" with providing a spot for a middle name, they're not enforcing it at this point.