Federal authorities have officially saved Minneapolis-St. Paul’s nonstop flight to Japan in a decision that was signed Thursday.

As a result, Delta Air Lines said it will switch its existing flight between MSP and Tokyo’s Narita airport to Haneda airport beginning Oct. 29.

The U.S. Department of Transportation, dismissing a strong protest from American Airlines, finalized a preliminary decision from July to grant Delta the daily flight between MSP and Haneda, a move that protects the Twin Cities from losing its only nonstop flight into Asia.

“Delta’s MSP proposal represents the best way to maximize benefits with the one remaining daytime Haneda slot. The geographic Northern Tier position of MSP, and the advantages that this presents [ ...] continue to represent significant public benefits,” the department said in its final order.

For MSP passengers to Tokyo, the flight to Haneda will shave some commute time because the airport is about 45 minutes closer to the central city than Narita.

In February, an aviation agreement between the U.S. and Japan opened up five daytime routes for U.S. carriers into Haneda. The airport previously was only open to U.S. airlines for night slots. Four of the five slots were set aside for existing nighttime routes that will be transferred to daylight flying. MSP was awarded the only new daytime Haneda slot.

The department awarded Delta two of the five slots, while American, United Airlines and Hawaiian Airlines each received one.

Delta initially fought the February agreement. By partly opening the airport to daytime flying by U.S. airlines, the Atlanta-based carrier argued that the department was giving its competitors an advantage. United and American have alliances with Japan’s two large airlines (and therefore more connecting flights), leaving Delta to do more of its own flying. These partnerships allow Delta’s competitors to feasibly operate a split hub, with some U.S. flights landing at Haneda and others at Narita, whereas Delta is more dependent on nonconnecting travelers if Haneda becomes more popular.

Delta warned that its hub at Narita could unravel in the wake of these changes. That process has begun; Delta canceled three nonstop flights from Asian and U.S. cities to Narita last month.

This threat rallied Minnesota politicians and business leaders to lobby the department on behalf of Delta. The entire Minnesota delegation petitioned Transportation Secretary Anthony Foxx, Minnesota Gov. Mark Dayton flew to Washington D.C. to meet with the department, and business coalitions wrote letters to the Obama administration.

American mounted a strong attack of the department’s tentative decision in July to award the new slot to Delta rather than to American for service at Dallas-Fort Worth, its hometown hub.

The department addressed each of its main points and all of Delta’s rebuttals in its final order, but ultimately stuck with its decision, stating the MSP proposal “would enhance geographic diversity” and further competition “by presenting a Midwest alternative” to Japan-based All Nippon Airways’ Chicago-Haneda service. Government officials also “took note of the potential competitive benefit of awarding a second slot to Delta, the one remaining applicant in the proceeding for the fifth available daytime slot that lacks a Japanese alliance partner.”

Peter Carter, chief legal officer of Delta, who thanked the Twin Cities community for its “unwavering support,” said it will feed its MSP-to-Haneda flight from more than 110 U.S. cities. Its Los Angeles-Haneda flight will connect passengers from 35 U.S. cities, he said.