The average U.S. domestic airfare declined 5 percent year over year on an inflation-adjusted basis to $352, the lowest first-quarter fare since records began in 1995, according to the U.S. Department of Transportation. That amount does not include ancillary fees, and fares accounted for 73.7 percent of total airline revenue during the quarter. The average one-way fare was $256, and the average roundtrip fare was $417 in the first quarter.