NOTE 2. REVENUE RECOGNITION Passenger Revenue Passenger revenue is primarily composed of passenger ticket sales, loyalty travel awards and travel-related services performed in conjunction with a passenger's flight. Ticket settlement occurs in periods subsequent to the sale of the related tickets at amounts other than the original sales price. Approximately $3.5 billion of the prior year air traffic liability related to passenger ticket sales (which excludes those tickets sold on behalf of other airlines) and was recognized in passenger revenue during each of the years ended December 31,2018 and 2017. Ticket Breakage. We estimate the value of tickets that will expire unused and recognize revenue at the scheduled flight date. a portion of the contract carrier's capacity and are responsible for selling the seat inventory we purchase. We record revenue related to our capacity purchase agreements in passenger revenue and the related expenses in regional carriers expense, excluding fuel. Loyalty Travel Awards Travel-Related Services adoption of the new revenue recognition standard, the majority of these fees were classified in other revenue. Required: 1. What percent of total passenger revenue in 2018 came from ticket sales? Note: Round your answer to the nearest whole percentage. 2. In which liability account does Delta record the sales of passenger tickets for flights that have not yet flown? 3. When does Delta recognize revenue of tickets that were purchased, but never used