Just received an email on this and below is the link to the web page explaining it.

Make this summer one of the most indulgent ones yet. For a limited time, get a 50% mileage discount toward a BusinessElite® upgrade.

For example, a flight from New York to Madrid, Spain, would normally require 15,000 miles for a one-way Upgrade Award from full fare Economy Class (Y fare class) to BusinessElite. With this offer's 50% discount, you would need only 7,500 miles to upgrade one-way to BusinessElite from full-fare Economy Class.

To qualify, purchase an Economy Class ticket in Y, B or M class of service on select transoceanic international flights. This 50% discount on mileage upgrades is also available on select international Business Class service to Mexico, the Caribbean, and South and Central America.


http://www.delta.com/skymiles/use_mi...TLUPGUPG-A-A-A