Spirit Airlines, Inc. is an American ultra-low-cost carrier, known for its extremely low base fares, but add-on charges for carry-ons, as well as checked luggage and hotels, are used to improve their bottom line.
In "The Boys in the Band", Chris hurries to catch a Spirit Airlines flight to see Ashley before she left.
Peter states at the end of "Passenger Fatty-Seven" that the plane they were on was from Spirit Airlines after Quagmire foils a hijacking and manages to avoid being destroyed after being shot down by the US government.
Seamus remains on hold with Spirit Airlines in the future timeline in "Rich Old Stewie".
Brian decides to hide his car, wrecked after drunkenly smashing into Mayor Wild West's hand-carved nativity scene in "Christmas Crime", in the Spirit Airlines parking lot, reasoning that it will be indistinguishable from the other clunker cars parked there. He also recalls flying with Spirit one time, during which all of the passengers fought for boarding positions.
When Mayor West mentions frontier spirit in "First Blood", Peter thinks he's talking about the airlines.
During the "This Old Town" number in "Adult Education", Meg mentions flying to Russia via Spirit Airlines.