The banner is flying on both Saturday and Sunday from Santa Barbara down to San Diego with a flight path along the coast (i..e over the long swath of beaches).
The marketing stunt also leads into another one of their "Monday Bunday" deals, where you buy one Mile High Bacon Thickburger and get another one for free with a date-specific coupon you can find online on their website. They'll put out a coupon each Monday through 10/27/14. Hardee's is also offering the same deal.
Photo via Carl's Jr.