A top United (UAL) executive last week reviewed the carrier's route system -- invariably said to be the best in the world -- and publicly defined the problem that has hobbled its performance for more than a decade.

"We built everything around focusing on international, which we do really well," said United President Scott Kirby. "But we let the domestic slide. {Today} United uniquely has less exposure to {domestic} markets than our competitors."

Kirby, who took over as president just six weeks ago, spoke at United's investor day on Nov. 15. It may have signified the turning point United has awaited ever since Stephen Wolf, its last great CEO, departed in 1994, as the carrier laid out a new path that includes boosting domestic flying, delaying aircraft orders and unveiling a plan for low-end seats that could lure passengers from ultra-low-cost airlines.

United is the only airline with hubs in the top five domestic markets of New York, Los Angeles, San Francisco, Chicago and Washington. Newark is the country's best trans-Atlantic hub, San Francisco is the best trans-Pacific hub, and Houston is the second best Latin America hub.

But domestically, United lags American (AAL) and Delta (DAL) , at a time when domestic profitability lags international profitability. The clearest sign of the gap is a consistently lower profit margin.

What happened? After domestic deregulation took effect in 1980, international markets remained largely regulated and profitable, Kirby said, while "domestic profitability plummeted," due to fragmented networks and a profusion of low-fare carriers. As a result, he said, "United's mindset {became}, 'we just want to fly enough domestic to feed our international flying.'"

In general, United's focus on international has led to cutbacks in domestic service. Kirby's principal illustration involved Newark, "the only true connecting hub in New York {and} the best Atlantic gateway of any hub in the country." United has about 400 daily Newark departures.

Before a 2010 merger, Continental and United jointly had about a 30% market share in New York. But now, the combined carriers have just a 26% share. "Our natural position is more like 30%," Kirby said. "There's no reason we shouldn't get back to that."

Not only does United lack New York market share, it also fails to take advantage of the potential to connect passengers.

American's Philadelphia hub, just 95 miles away, offers about 430 daily departures and does the same thing as Newark, connecting East Coast passengers to various destinations including the trans-Atlantic. Yet the Philadelphia hub connects 45% of its traffic, Kirby said, while the Newark hub connects just 35%.

Philadelphia's advantage, he said, is better connecting banks, where American's departures and arrivals are closely aligned. By contrast, in Newark, United more widely separates departures and arrivals. In airline speak, "rolling departures and arrivals create less connectivity."

While the industry commonly assumes that connecting passengers are lower yield passengers, Kirby contends the opposite it is true. "The most profitable hubs in the country have the highest percentage of connecting revenue," he said.

Kirby has said that Charlotte, where about 75% of passengers connect, is American's most profitable hub, in terms of profit margin. He said Denver, where about 40% of passengers connect, is United's most profitable hub. In both cases, low airport costs enable airline profitability despite locations that do not provide large numbers of originating passengers. (Delta's most profitable hub is Atlanta.)

Rebanking Newark to boost connectivity between smaller markets would challenge rivals, who could not reasonably match the service, Kirby said. For instance, "Albany to Charleston is such a small market, there is nothing for our competitors to do," he said. "We can win back our fair share in those markets. There is no reason we can't make Newark look like Philadelphia, just by timing flights correctly."

Kirby acknowledged that Newark presents unique operational problems, but said the intent is to alter the timing of flights, not to boost the number of flights.

Another example of United's pullback at Newark is that in 2004, Continental had eight mainline flights a day between Newark and Atlanta, while Delta had 11. By 2013, United had cut back to six daily flights, all on regional jets.

The short-term impact was beneficial: Operational costs declined and profits rose. But over time, Kirby said, "Passengers say 'I'd rather not fly on regional jets, I will switch to Delta.' Then you down-gauge more flights. And you spiral down {and} you cede the market to your competitor."

United recently reversed course: It now has six daily mainline flights between Newark and Atlanta.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.

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