A recent analysis of the world's 50 most underserved international airline routes by the air travel intelligence company OAG revealed that 19, or 38%, involved a U.S. destination.
The study, "Underserved Uncovered," which OAG released early this month, also underscored the complex set of financial and logistical criteria that airlines use in deciding which routes to serve and at what frequency.
In compiling the list, OAG ranked underserved routes by which had the greatest number of bookings that included stopovers last year. Some city pairs made the list even though they were served by nonstop service.
The city pair that topped the list was Jakarta, Indonesia, to Jeddah, Saudi Arabia, with 280,000 one-stop bookings in 2015.
The most underserved city pair involving the U.S. market ranked No. 2 on OAG's list: Some 239,000 one-stop ticket segments were purchased for flights between New York JFK and Tel Aviv. By comparison, 432,000 people flew nonstop between those airports.
The next four most underserved international routes involving the U.S. were Los Angeles-Ho Chi Minh City, Los Angeles-Manila, Los Angeles-Bangkok and San Francisco-Delhi, all of which made the top 12.
In a Travel Weekly interview, OAG analyst John Grant said there are many reasons that routes can appear to be underserved. For example, airlines sometimes struggle with a shortage of aircraft.
In addition, a route, while popular, might not draw premium prices, making it less desirable for an airline to offer on a pure margin basis. And sometimes passengers simply choose to take a stopover in order to get lower fares or more loyalty points.
With 19 routes on the underserved routes list, the U.S. nearly doubled the next country on the list, Thailand, which featured in 10 of the airport pairs.
The distance between the U.S. and many large Asian markets and the heavy reliance of U.S. carriers on domestic hubs are reasons why the U.S. has so many of the underserved international routes, the OAG authors wrote. The sheer size of the U.S. market and the number of people flying in and out of the country is also a factor.
Still, some analysts questioned how OAG chose to define underserved routes.
"That's kind of an odd construct," said Bob Mann of R.W. Mann & Co. Agreeing with Grant, Mann said that in many cases, customers intentionally choose indirect over direct itineraries. In addition to going after frequent flyer points, business travelers also do it in some cases because their companies require that they fly specific carriers.
Mann pointed to OAG's second-ranked route in the underserved list, New York JFK-Tel Aviv, which is currently serviced by El Al and Delta, with a total of nine flights per week.
"I would hardly say that it is underserved," he said, adding that business travelers often choose to make European stopovers between New York and Israel.
Seth Kaplan, managing partner of the newsletter Airline Weekly, said that the analysis does not touch on the crucial consideration of what people are willing to pay for a flight.
"In terms of the market itself, airlines are going to be looking at passenger volume but also yield," Kaplan said.
Leisure-focused routes might have plenty of demand, but fewer passengers are willing to pay for business-class seats or even for a pricier coach fare compared with business passengers on routes that serve centers of commerce. Ultimately, factors like that drive the decisions of airline route planners.
Illustrating Kaplan's point is Thailand, a mostly leisure market that factors in 10 of OAG's top 50 underserved routes. Kaplan noted that by comparison, Singapore, a world business center, doesn't appear once on the list, even though it is close to Thailand geographically and even though both countries have strong bilateral air service agreements around the globe, meaning that they are not heavily constrained by protectionism and red tape.
"It is absolutely because they are very opposite in terms of the profile of the market," Kaplan said.
Still, other complexities also factor into airline route planning.
Notably, nonstop flights weren't offered at all in 2015 on four of the city pairs involving the U.S. that made the OAG underserved list. Three more such routes aren't being serviced directly this summer.
Among those 2015 routes were two to Vietnam's capital, Ho Chi Minh City, one from Los Angeles and the other from San Francisco. According to an April 2015 article in the publication Airline Reporter, Vietnam Airlines has said it would like to fly to Los Angeles. (The airline couldn't be reached for comment.) Before that could happen, however, the country of Vietnam would have to be certified by the FAA for its airline oversight practices.
In the meantime, U.S. carriers could fill in the void on those Ho Chi Minh City routes, but Kaplan said they have to decide whether doing so is worth it given the length of the flight and the nature of U.S.-Vietnam market, which centers on diaspora and leisure travel.
The OAG study singled out India as the largest underserved country market to and from the U.S., with 404,000 one-stop bookings in 2015 across the three U.S.-India top 50 underserved routes.
Seeing that opening, Air India last December added three weekly direct flight on the most traveled of those city pairs, San Francisco-Delhi.
But neither Air India nor any other carrier currently flies direct between one of the other two pairs: JFK and Mumbai. (It does service Mumbai from Newark, as does United.)
In an interview, Air India Americas manager Vandana Sharma cited the carrier's limited number of long-range aircraft as the key limitation in expanding its U.S. route network.
"We are actively evaluating possible new routes, and we are taking delivery of aircraft," she said. "As the position improves, we will be adding new routes."