Many consumers aren’t aware that when they search for a low airfare with an online travel agency (OTA) such as Travelocity or a popular search app such as Hopper, Kayak or Farecompare, they may not be seeing the lowest possible airfares.

In fact, if they use these sites to buy airfare from or to an airport such as Minneapolis-St. Paul, where Delta commands over 70 percent of the market, or Kansas City, where Southwest controls 50 percent of traffic, it’s almost certain many of them will pay more than they should.

But don’t blame the aforementioned websites and apps. Instead, blame the airlines themselves.

Delta and Southwest, which together control about 35 percent of U.S. domestic seats, are the main culprits here. Southwest, which rarely used to display its airfares anywhere other than Southwest.com, one would expect. But Delta is a relative newcomer to the airfare hide-and-seek game. The Atlanta-based carrier now withholds its airfare data from sites such as Trip­Advisor, Farecompare and Hopper among others (American Airlines in the past has withheld its fare data from OTAs such as Orbitz.com).

So many consumers are not getting the full airfare picture and it’s much harder to compare prices; many are overpaying for flights, or simply cannot afford to fly unless they know where and how to search.

It’s impossible to calculate how much this costs uninformed consumers, but it’s certainly in the millions each year. One day I was searching for a flight between Austin, Texas, and Newark, N.J.; on Southwest.com the dates and flight times I decided on would cost $216 round-trip, while the least expensive comparable itinerary on United found via Google Flights, which doesn’t include Southwest, was $763 round-trip.

Am I suggesting that the government force airlines to share their data? Not exactly. Although the U.S. Department of Transportation is looking into the issue of airlines withholding prices from third-party websites and apps, the airlines shouldn’t be singled out here.

As Vaughn Jennings, spokesman for Airlines for America, the lobbying group for U.S. airlines, told the Star Tribune’s Kristen Leigh Painter in January, “We continue to believe that airlines, like all other private businesses, have the right to sell their product where and how they choose.”

Sad to say, he has a point. There are precedents. Some hit songs are only available on iTunes, or not on iTunes (think back to the many years that the Beatles catalog was withheld from Apple’s music service). Fashion designers such as Marc Anthony can negotiate exclusive marketing deals with retailers such as Kohl’s, and Martha Stewart can decide to sell her products exclusively at Kmart.

It’s a bit of a false equivalence, though. No consumers are overpaying because of these other marketing agreements. Show me the shopper who cares that, or who has suffered a financial hardship because, she cannot buy a Louis Vuitton handbag at Target.

What I am suggesting is that OTAs and meta search engines should transparently acknowledge on their websites and during telephone sales calls that they are being forced to hide information from consumers. Many consumers understandably assume that when they go to an airfare comparison website or app they will compare all airlines. Hence Kayak’s “Search one and done” slogan.

But government regulation? Let’s be real. With new leadership in Washington we’ll be seeing fewer, not more, fetters placed on businesses. So it’s consumer beware and be wise.