<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Booking codes for AA revised for domestic flights: AA DOMESTIC FLIGHTS 3000-5999 First: Y Business: Y Economy: L</font>
Those would be American Eagle flights, which only have a Y cabin. At least for A & D fares there will not be the availability issue that there used to be when those segments had to be booked in M/L.