This article combines data from 4 sources with slightly different data. Airfares were flat at the end of the 20th century, but then dropped by 19% by 2004. They remained flat, in real terms, through 2009. Airlines pushed through 8% higher prices in 2010-11 and maintained real fares at the same level through 2014. After 19 years, real airfares were 14% lower than in 1995.

Fares then dropped year after year through 2019, reaching 26% below the 1995 baseline. They have fallen further in the pandemic years to 43% below the level of 25 years ago.

Bureau of Labor Statistics / CPI

The Bureau of Labor Statistics compiles a consumer price index for air travel as part of the overall CPI. It compiles average prices and tries to adjust for changes in the quality of the product.

https://data.bls.gov/timeseries/CUUR0000SETG01?output_view=data

https://www.bls.gov/cpi/factsheets/airline-fares.htm

https://www.bts.gov/content/annual-us-domestic-average-itinerary-fare-current-and-constant-dollars

https://fred.stlouisfed.org/series/CPIAUCSL#0

https://fred.stlouisfed.org/series/CUSR0000SETG01#0

Bureau of Transportation Statistics

https://www.bts.gov/newsroom/figure-1-us-average-domestic-annual-fares-1995-2020

BTS graph and 20 more about the airline industry.

https://www.airlines.org/dataset/the-air-travel-value-proposition/

BTS: Revenue Per Passenger Mile

https://www.bts.gov/content/average-passenger-revenue-passenger-mile-indexes

Dept of Transportation: Average RoundTrip Fares

https://www.airlines.org/dataset/annual-round-trip-fares-and-fees-domestic/

Prior 25-50 Years

Real airfares declined consistently throughout the period, but no data source is fully compatible with the 4 summarized above. It appears that the real cost of flying declined by about one-third between 1979 and 1995 as the airline industry was deregulated.

Even with Fees, the ‘miracle of Flight’ Remains a Real Bargain; Cost of Air Travel per Mile Has Fallen by 50% Since 1980

The Cost of Air Travel in the US Has Been Remarkably Stable for the Last Decade, and 17% Cheaper Than 20 Years Ago

https://www.travelandleisure.com/airlines-airports/history-of-flight-costs

https://simpleflying.com/50-years-airfares/

https://www.travelandleisure.com/airlines-airports/airfare-cost-change

See How the Cost of a Flight Has Changed Since 1963 [Charts]

Air Industry Productivity (How’d they do it?)

https://www.econlib.org/library/Enc1/AirlineDeregulation.html

Crowds in the air

https://www.bls.gov/opub/mlr/2017/article/economic-productivity-in-the-air-transportation-industry.htm