"These seven performances of Traviata are hopelessly overbooked," said box office director Adreas Vrtal.
The production stars Anna Netrebko, Rolando Villaz‹n, and Thomas Hampson.
Sales are also strong for a new production of The Magic Flute, to be conducted by Riccardo Muti; Schreker's Die Gezeichneten; and Pina Bausch's Nelken.
The festival runs from July through August 31, and will include 183 events.