Earlier this year, the governments of the U.S. and Japan struck a deal to permit new flight paths near a Tokyo-area Air Force base. This modification will increase the capacity of nearby Haneda International Airport: the airport closest to Central Tokyo.

As part of the agreement, U.S. airlines will be able to add 12 new daytime international flights from Haneda Airport beginning in the spring of 2020. American Airlines (AAL -0.22%), Delta Air Lines (DAL -0.28%), Hawaiian Holdings (HA), and United Continental (UAL -0.17%) all want to get in on the action.

Check out the latest earnings call transcripts for United Continental, Hawaiian, Delta, and American Airlines.

The airlines finally get what they want

In late 2010, U.S. carriers gained access to Haneda Airport for the first time in more than three decades. The same four airlines fought vigorously over the four available slot pairs (permitting a total of four roundtrip flights). However, they were limited to overnight takeoff and departure slots at Haneda -- between 10 p.m. and 7 a.m. -- which made most of the routes commercially unsuccessful. The only real exception was Hawaiian Airlines' flight to Honolulu.

In late 2016, U.S. airlines finally got an opportunity to begin serving Haneda Airport during the day. There are currently five slot pairs for daytime flights by U.S. airlines. American Airlines flies to Los Angeles, Delta flies to Los Angeles and Minneapolis-St. Paul, Hawaiian flies to Honolulu, and United flies to San Francisco. There is also one remaining nighttime slot pair, which Hawaiian Airlines uses for additional flights to Hawaii.

A Delta Air Lines A330 jet landing on a runway

Delta holds two daytime slot pairs at Tokyo's Haneda Airport today. Image source: Delta Air Lines.

All of these daytime routes have been successful. Not surprisingly, the airlines are eager for more daytime flights at Haneda Airport -- and under the new agreement between the U.S. and Japan, they will collectively have 17 daytime slot pairs there, up from just five today.

Looking at the airlines' requests

The 12 new daytime slot pairs at Haneda Airport will be distributed by the U.S. Department of Transportation (DOT) based on an analysis of the public benefits of each proposed flight. That includes an analysis of which proposed flights would best serve the traveling public, and which ones will foster increased competition. The four airlines requested a combined total of 19 round-trip frequencies, so the DOT will have to pick and choose which flights to permit.

Delta Air Lines and United Airlines each requested six daily frequencies. Delta proposed daily flights to Atlanta, Detroit, Portland, and Seattle, as well as twice-daily service to Honolulu. Meanwhile, United proposed daily flights to Chicago, Guam, Houston, Los Angeles, Newark, and Washington, D.C.

American Airlines had a more modest proposal. It requested four frequencies to permit twice-daily service to Dallas-Fort Worth, a second daily flight to Los Angeles, and a new route to Las Vegas. Lastly, Hawaiian Airlines would like to add three additional daily flights to Honolulu.

What will the DOT decide?

Hawaiian Airlines says additional flight times would help it inject new competition into the Japan-Hawaii travel market by enabling more connections at Haneda Airport. As a result, the DOT will likely award it an extra daily flight to Honolulu. But with the carrier currently seeking a joint venture with No. 2 Japanese carrier JAL that would dominate Japan-Hawaii travel, the DOT probably won't want to give any more slots to Hawaiian.

Delta argues that all six of its requests should be granted, because American and United have joint ventures with the two big Japanese airlines, giving their customers ample access to Haneda Airport already. There's a pretty strong case for the four mainland routes it has requested. The first Honolulu flight also has a decent chance of approval, as it would boost competition in the massive Tokyo-Honolulu market. The second flight to Honolulu seems like a stretch, though.

That leaves perhaps six frequencies to divide between American and United. United's top three choices of Newark, Chicago, and Washington are all likely to be approved. American's top priority of Dallas-Fort Worth also seems like a lock.

A United Airlines Dreamliner jet flying over a coastline

United is likely to be awarded several more slot pairs at Haneda Airport. Image source: United Airlines.

For the last two slot pairs, the DOT would have to weigh some difficult trade-offs. United is the only U.S. carrier that doesn't fly from Los Angeles to Haneda today. Additionally, its proposed Houston and Guam routes would be the only flights from those cities to Haneda. On the other hand, including its partner ANA, it already has the most Haneda-U.S. slots.

Awarding American Airlines at least three slot pairs would help maintain the overall competitive balance. But American's second- and third-priority routes are simply additional frequencies to Los Angeles and Dallas, respectively. The DOT might prefer to spread the flights around by choosing American's lowest-priority route (Haneda-Las Vegas) and one of United's other proposals, either Guam or Houston.

It will take a good chunk of the year for the DOT to sort through all of the airlines' arguments and make a final decision. But in the end, American Airlines, Delta Air Lines, Hawaiian Holdings, and United Continental should all be winners.