APA uses an system. If no individual author is listed, use the airline or organization as the author.
Airline Name. (2017). Title of the promotional offer or article . Website Name. URL. In-Text Citation: (Airline Name, 2017). MLA Style (9th Edition) buy one get one free airline tickets 2017
"Title of the Webpage." Title of the Website , Publisher [if different], Day Month 2017, URL. In-Text Citation: ("Title of the Webpage"). Chicago Style (17th/18th Edition) Author–date citation system - APA Style APA uses an system