Originally Posted by
FWAAA
You're technically incorrect.
The current limit was imposed in early October, 2001, by edict from Norm Mineta, then-Sec of Transportation (following input from an industry task force, which included Bob Baker of AA). All airlines were required to modify their carry-on policies to his edict and they've remained there ever since.
The FAA rule, now a formal FAR, is that each carrier have and enforce a carry-on baggage policy. The one-plus-one-item verbiage was strong-armed into place through talk and decree, not legislation or regulatory process.
Airlines still do not have a uniform definition of personal item (AA's is much more liberal than US's, for instance), and some (like AA) have a further list of supplemental items not counted against the one-plus-one limit. Recently, through further FAA pressure, the big five consolidated their policies on a main carry-on size limit of 45 inches. It is not uniform across all carriers, however.