Through August 31, United is offering those with addresses in Illinois and California double elite qualifying and redeemable miles for roundtrip travel between Chicago and Los Angeles and Chicago and San Francisco. The offer is only valid for flights booked and flown between May 19 and August 31. Registration is required.
Obviously this is a response to American’s double miles promotion, which is a response to Virgin America starting service to Chicago. It’s worth noting, however, that American doesn’t require the actual itinerary to be between the city pairs above. While United only awards the double miles if you’re traveling between Chicago and Los Angeles or Chicago and San Francisco, American will award the bonus miles if a segment between those cities is part of a larger itinerary. So while American’s offer is much more generous, I can see why United wouldn’t include those with itineraries including that segment. I think the thing that will irk most people is that previously booked travel doesn’t qualify.