The U.S. Department of Transportation (DOT), in a bit a surprise, has fined TripAdvisor $80,000 for violating government rules on full-fare advertising, the first penalty for violating the its new airline price advertising requirements that took effect in January, as well as for failing to disclose that flights were being operated under code-sharing agreements. The company was also ordered to cease and desist from further violations. TripAdvisor is better known for its hotel reviews, but it also has an airline-booking engine.

The DOT noted that it requires all advertisements that include airfares to state the entire price to be paid by the consumer. Prior to a rule that took effect Jan. 26, advertised fares were not required to include certain government-imposed taxes as long as these additional fees were clearly disclosed in the ad, but under the new rule all government taxes and fees must be incorporated into the fare. Taxes that are included in the advertised fare can also be listed separately or through links or pop-ups, but these listings may not be displayed as prominently, or in the same or larger size font, as the total price.

The DOT said an investigation by its Aviation Enforcement Office found that from at least March 2012 through June 2012, the total fares displayed on TripAdvisor’s website were not displayed more prominently than the base fares, which did not include taxes and fees. When consumers entered specific itineraries, TripAdvisor also returned lists of flights that displayed base fares in front of and in the same font size as the total fares. The rule applies to ticket agents as well as air carriers.

The DOT also found that TripAdvisor failed to comply with DOT’s code-share disclosure rules. Government rules require airlines and ticket agents to disclose to consumers before they book a flight, if the flight is operated under a code-sharing arrangement. The disclosure must include the corporate name of the transporting carrier and any other name under which the flight is offered to the public.

Under a new law, the DOT said, when tickets are purchased on the Internet, code-share information must be easily viewable on the first display of a website following a search for flights corresponding to a desired itinerary. From at least March through June 2012, TripAdvisor failed to display the corporate names or other names being used by regional carriers providing transportation on behalf of a major airline. Consumers had to rely on a hover text feature to learn the identity of the airline that would actually operate the aircraft on which they would be flying.