This is the inflation-adjusted, roundtrip airfares since 1995.
shows the gradual decline in average US round-trip, inflation-adjusted airfares, which have fallen by nearly 30%, from $485 in Q1 1995 to $347 in Q4 2017 (in 2017 dollars), inspired by the article by Robert Poole in the June issue ofReason Magazine“If You Can Afford a Plane Ticket, Thank Deregulation“:
In 1979, the first year of deregulation, the average domestic fare was $616 (in 2016 dollars), or 1.2% of average household income that year. The most recent comparable data I can find is for 2016, when the average fare was $344—a mere 0.6% of average household income.
So after adjusting for both inflation and increases in average household income, the cost of air travel in the US has fallen by 50% since deregulation.