Delta has a new promotion that promises a $150 gift card or a free upgrade if you take 2 round-trips.
Register now, then book and fly any two round-trip flights on Delta or Delta Connection® marketed and operated flights between now and July 3, 2014, to earn your choice of:
A $150 American Express® Reward Card OR
A confirmed upgrade to First Class or BusinessElite® on one-way travel; within the continental U.S. (including between JFK and SFO/LAX/SEA)
Pick your preferred reward and register now to get started.
I wasn't targeted apparently and could not register but maybe it works for you?