Smith raised a stink about the incident on his Twitter page Sunday, saying "I'm way fat, but I'm not there just yet," and "If you look like me, you may be ejected from Southwest Air." He posted a picture of himself sitting on the plane with his cheeks puffed out.
Southwest says it "Customer of Size" policy require travelers must be able to fit safely and comfortably in one seat or make other arrangements.
After a storm of angry online comments from Smith and his fans, the airline issued an apology first from its own Twitter account and later in a statement on its Web site titled "Not So Silent Bob," a jovial jab at the Silent Bob character Smith plays in many of his films.
"We would like to echo our tweets and again offer our heartfelt apologies to you," the statement said.
The airline said it also accommodated Smith on a later flight, gave him a $100 voucher and apologized by phone.
Both Smith and the airline acknowledged that he had bought two seats for his original flight from Oakland, where he had spoken at the Macworld Expo conference.
But he was flying standby in order to catch an earlier flight, and only one was available.
Smith insisted that he was still able to put both armrests down and buckle his seat belt, which is Southwest's standard.
Smith is the director of the new Bruce Willis movie "Cop Out," and previously directed the films "Clerks" and "Chasing Amy."
