Domestic airline fares have been trending downward for the past 15 years or so, according to government statistics. As a matter of fact, fares are as cheap now as they were five years ago. And adjusted for inflation, they are down by 20% since 1995.

But at the same time, U.S. airlines have been reporting steadily higher profits in recent years. How can this be?

The latest report from the Bureau of Transportation Statistics (BTS) says that the average domestic air fare in the fourth quarter of 2015 fell by 8.3 percent from the same quarter a year earlier, from $396 to $363.

Over the longer term, the decline is even more substantial. According to BTS, the average fourth quarter domestic air fare, adjusted for inflation, fell by 18.2 percent from 1995 to 2015.

For the full year 2015, BTS said, the average fare fell by 3.8 percent from 2014, to $377 – its lowest level since 2010. Adjusted for inflation, the 2015 average fare was 19.2 percent less than the record annual high of $467, recorded in 2000.

So why are the airlines swimming in black ink these days? A big part of it, of course, is the reduced operating cost they enjoy thanks to the precipitous decline in oil prices over the past couple of years. And another big part of it is the industry’s eager embrace of all kinds of ancillary fees that passengers didn’t have to pay 20 years ago. For example, BTS data shows that Delta, American/US Airways and United each took in more than $600 million in those onerous change and cancellation fees in the first three quarters of 2015.

Twenty years ago, BTS said, U.S. airlines collected 87.6 percent of their total revenues from passenger fares. By the third quarter of 2015 (the latest data available), that figure had dropped to 75 percent.

The most recent report on airlines’ ancillary fees from IdeaWorks/CarTrawler, which came out last fall, estimated that airlines worldwide brought in almost $60 billion in non-airfare revenues, almost tripling their take from that source in just five years. And the major U.S. airlines accounted for more than 30 percent of the total.

For the typical major U.S. airline, a little more than half of ancillary revenues came from the sale of frequent flyer miles. Most of the rest came from baggage fees and “a la carte” fees charged to passengers for amenities and services that were largely included in the air fare several years ago, or didn’t exist back then (like in-flight Wi-Fi fees).

“The a la carte category grew to 20% due to more emphasis placed upon comfort-related services such as premium economy seating, buy-on-board food, and priority screening and boarding,” IdeaWorks said. Another 20 percent came from checked baggage fees.

So when the airlines boast that we are paying less in air fares these days, that’s technically true – but it doesn’t necessarily mean we are paying less for air travel.

NOTE: Be sure to click here to see all recent TravelSkills posts about: United’s newest, longest flight + Tipping Uber drivers + Qantas 747 Trip Report + Confusion over PreCheck policies + No-fee earlier flights

Do you follow us on Twitter? It’s a great way to keep up with the latest news!

Please join the 125,000+ people who read TravelSkills every month! Sign up here for one email-per-day updates!