Title 14

[CFI A&P]

Air commerce means interstate, overseas, or foreign air commerce or the transportation of mail by aircraft or any operation or navigation of aircraft within the limits of any Federal airway or any operation or navigation of aircraft which directly affects, or which may endanger safety in, interstate, overseas, or foreign air commerce.

Air transportation means interstate, overseas, or foreign air transportation or the transportation of mail by aircraft.

What's the difference? Commerce means it affects federal space but Transporation means general air shipping?

Not all transportation is considered commerce. In a very general sense - Elon Musk bombing around in his jet is transportation but it isn't commerce. That can get really deep as to whether the airplane is used for charter, IRS implications, etc., but for now just think of as private transportation not engaged in commerce. Whereas American, Delta, Southwest, et al are engaged in commerce while providing transportation. Later on in Part 61 you'll read a regulation that refers to privileges of an airman's certificate with regard to commerce that is often misquoted.