The first automated airline reservation system dates back to the 1960s.

Ever since, travel agents have tapped into this data to help travelers compare prices across multiple airlines, search seat availability and book tickets.

In 2005, Chris Lopinto saw an opportunity to aggregate this data into a one-stop shop for frequent fliers and business travelers. With his father, John, and uncle, Joseph, he launched Patchogue-based ExpertFlyer.com.

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The subscription-based site provides travelers with access to in-depth, real-time airline information, from fares and seat maps to seat inventory available for awards (such as frequent-flier miles) and upgrades — information they can’t find on free travel websites such as Orbitz or Kayak. The site has general flight information for about 400 airlines and information on award and upgrade availability for about 70 airlines.

Lopinto, 36, said the company is working to expand its award and upgrade information but has faced some turbulence from the airline industry along the way.

“The airlines hold their data very close to the vest,” he said.

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In the beginning, and still to some extent, the company has had to convince airlines that it’s not trying to compete with them, he said. ExpertFlyer.com doesn’t sell tickets or book travel but rather aggregates data by tapping into multiple global distribution systems (GDS), services that distribute airline data to travel agents. “It’s always an ongoing work in progress to educate the airlines,” said Lopinto.

One expert said this isn’t surprising.

“Content has value,” said Robert Mann, president of Port Washington-based R.W. Mann & Co., an airline industry analysis firm.

The airlines may not want certain flight information circulated by a third party if they don’t “see a corresponding benefit,” said Mann, noting “this is a battle for control of content.”

When ExpertFlyer first launched, Lopinto said, he fielded multiple queries from airlines concerned about the site.

That has died down, and over the years the company has created relationships with some airlines that provide ExpertFlyer with information beyond what it could pull from airline reservation systems. One such airline, American Airlines, did confirm it has a relationship with ExpertFlyer, but declined to comment further.

Still, the site faces resistance from at least one carrier, Delta Air Lines, which Lopinto said asked ExpertFlyer to remove Delta’s flight information in the fall of 2014. ExpertFlyer complied, fearing Delta would ultimately take steps to prevent the company from seeing its data in the GDS. This past December though, he said, ExpertFlyer began adding back Delta flight information by tapping into a non-GDS source.

Delta didn’t respond to requests for comment, and some other carriers declined to comment or didn’t respond to a general inquiry from Newsday on the service ExpertFlyer provides.

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Still, there is demand for this type of information, particularly for those booking award travel, said Mann.

“Knowing the availabilities beyond what the carrier will display to you, which is really a yes or no display, is more informative,” he said.

A carrier may display if there is availability to use your miles to book award travel or upgrades, but not display the total number of these tickets available per flight, said Lopinto.

With ExpertFlyer, travelers can set an alert so they will be informed when award and upgrade availability opens up on a particular airline, as well as when a particular fare class or seat becomes available.

“I use that all the time,” said Ray Watson, vice president of global technology for Dallas-based Masergy Communications, who travels approximately 150,000 miles per year.

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Travelers like Watson pay a subscription fee to access the site ranging from $4.99 to $9.99 per month or $100 annually depending upon the plan. There is a free version that allows a user to set one free seat alert at a time, said Lopinto.

“For people who travel a lot, it cuts through a lot of the clutter,” noted Watson.

Down the line, ExpertFlyer wants to include even more award/upgrade inventory and might even branch out into other travel data beyond air, said Lopinto.

“It’s an ongoing process, but now we’re at the point where we’ve established an equilibrium with the industry,” he said.