From
http://www.delta.com/skymiles/about_...ules/index.jsp...
Duplicate or Conflicting Reservations
The booking of duplicate or conflicting reservations for Award Travel is prohibited. Delta reserves the right to cancel any duplicate or conflicting reservation without notice.
From the Contract of Carriage, Rule 115 (at
http://images.delta.com.edgesuite.ne...rriage_dom.pdf):
E) Fictitious Bookings
Multiple bookings of a fictitious nature are prohibited by Delta. In the event Delta determines that an individual has confirmed such bookings to one or more destination(s) on or about the same date(s), the carrier reserves the right to cancel all confirmed space associated with the multiple reservations without notice to the passenger or the person making the booking.