A further update...YUR appears to be the three-letter code in Sabre for Aerosur, whose 2-letter IATA code is 5L.
Aerosur = COMPANIA BOLIVIANA DE TRANSPORTE AEREO PRIVADO S.A.
Hmmm...an error on AA's part, me thinks...
[This message has been edited by 777Brit (edited 04-01-2003).]