Delta Air Lines (DL, Atlanta Hartsfield Jackson) has been allowed to retain its Seattle Tacoma International-Tokyo Haneda slot pair by the US Department of Transportation (DOT) following an inquest precipitated by rivals American Airlines (AA, Dallas/Fort Worth) and Hawaiian Airlines (HA, Honolulu).

Late last year, American and Hawaiian petitioned the DOT to strip Delta of the route following its decision to operate only 17 return flights between Seattle and Tokyo Haneda from October 1, 2014, until March 28, 2015. In its initial finding, the DOT said the reduced service, whose overall frequency was only just enough to prevent the Department's 90-day dormancy condition from kicking in, 'severely undercut the public interest' thereby warranting an inquest.

However, despite proposals from American (a year-round, daily return Los Angeles International-Tokyo Haneda service) and Hawaiian (a year-round, daily return Kona-Haneda service), the DOT upheld its original 2013 decision to award Delta the Haneda slot pairing on the grounds that it was and still is the best possible use of the coveted slot. But, in order to ensure its full use, the DOT has now attached stringent conditions and protective measures designed to ensure Delta operates the route as a year-round daily service.

"Any failure, without a Department-granted waiver, to perform a Seattle-Haneda flight, and any failure, without a Department-granted waiver, to perform a Haneda-Seattle flight, on each and every day of every week (7 days a week, 365 days a year), will constitute a violation of Delta’s Seattle-Haneda authority subject to enforcement," the DOT said in its decision. "Any failure, without a Department-granted waiver, to perform Seattle-Haneda flights, and any failure, without a Department-granted waiver, to perform Haneda-Seattle flights, on two days of any seven-day period (365 days a year) will constitute a default of Delta’s Seattle-Haneda authority and that authority will automatically expire."

Furthermore, Delta will be required 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. The reports will then allow the DOT to assess Delta's use of the slot and, if necessary, allow for its reallocation to American Airlines whose original proposal (outlined above) has now been selected as a backup.

Despite the stringent new conditions attached, Delta has reaffirmed its commitment to the route, returning it to a year-round, daily B767-300-operated service as of March 29.

"Delta thanks the U.S. Department of Transportation for its tentative decision to allow the airline to continue its service between Seattle and Haneda Airport in Tokyo," the carrier said in a prepared statement. "Earlier this month, Delta resumed its nonstop service between Seattle and Haneda after a temporary seasonal suspension. Delta will operate year-round, nonstop flights between Seattle and Haneda as we continue to grow Delta's international gateway at Seattle-Tacoma International Airport."