Delta Air Lines (DL, Atlanta Hartsfield Jackson) has announced it will relinquish one of its two Tokyo Haneda slots to the US Department of Transportation (DOT) for reallocation with effect from October 1, 2015.

In a letter to the DOT, the carrier said the seasonality of its Seattle Tacoma International-Tokyo Haneda route rendered it uneconomical to operate as a year-round daily service and as such, its final flight on the route would be on September 30.

"We have determined that it is not commercially feasible to operate the slots allocated to Delta for Seattle-Haneda service on a consistent daily basis year-round because: (i) demand for Seattle-Haneda service is highly variable, peaking in the summer and declining in the winter; and (ii) Delta lacks a Japan airline partner to provide connectivity beyond Haneda to points in Japan and other countries in Asia," it said.

Following a route case proceeding brought by American Airlines (AA, Dallas/Fort Worth) and Hawaiian Airlines (HA, Honolulu) late last year contesting Delta's move to operate its Seattle-Tokyo Haneda route as a seasonal service, the DOT agreed to allow Delta to retain the route albeit as a daily year round operation under several strict conditions. The measures include pain of slot-revocation should Delta fail to operate a single flight without a Department-granted waiver. Further to that, Delta would also have to submit quarterly reports to the DOT detailing its use of its Haneda slot pair - in particular any failure to operate its Seattle-Haneda flights with a detailed explanation to boot.

Delta subsequently rejected the terms as "impermissible, arbitrary and capricious" warning they would 'impose serious burdens on Delta and the public interest with no countervailing justification.'

The DOT in its response rejected those allegations claiming its conditions were merely an enforcement of the very same conditions Delta agreed to when it first applied for route authority.

"...the Department finds that the condition, as proposed, is reasonable and necessary to ensure that the public benefits of Seattle-Haneda service, benefits that were central to the Department’s original decision to select Delta at Seattle, and to its tentative decision to continue Delta at Seattle, can be realized," it said.

"The Department finds no convincing basis to conclude...that a condition calling upon Delta to do precisely what Delta itself committed on the record to do – provide year-round daily Seattle-Haneda service – would somehow qualify as 'draconian,' 'extreme,' 'patently overbroad,' 'arbitrary,' 'capricious,' and 'plainly unlawful.'"

As such, Delta has agreed to relinquish the slot which, according to the DOT's route case proceeding ruling, now falls to American Airlines (AA, Dallas/Fort Worth). American has said it would use the slot to operate a daily B777-200(ER) service between Los Angeles International and Tokyo Haneda.

Delta will continue to serve Tokyo Haneda with a daily B767-300(ER) flight from Los Angeles.