Originally Posted by pk45cu

U isn't just a Ted fare. UA has been using E and U class for fares that match DL SimpliFares and the new AA fare structure. The UA E and U typically match the DL Y and B fares, and the AA Y and K fares.

The new AA fare structure has Y and K fares on most routes for unrestricted tickets. Think of K as having all the features of Y, except it's inventory controlled.