“Domestic Round-Trip Fares and Fees: Average Domestic Round-Trip Airfare: Nominal & Real2018”, Airlines for America2018 (economics; backlinks)⁠:

The table below offers a time series of the average domestic round-trip airfare as reported by US passenger airlines to the U.S. Department of Transportation¹. Included in the table are the average base fare, the average bag and change fee revenue per passenger, and the combined average “all-in” base fare. All metrics are expressed in both current and inflation-adjusted dollars (2017) and does not include government-imposed taxes and fees…

1990, all-in roundtrip fare: $677.11^$556.03₂₀₁₇…2018: $440.99^$362.13₂₀₁₇.

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