Delta has asked the US Department of Transportation (DOT) to revoke American Airlines' newly-acquired flight rights to Tokyo Haneda.
In mid-June, the DOT granted American the right to launch a route between Los Angeles and Haneda (see news, June 19).
It had 60 days to start the service, which Delta now claims American has failed to adhere to.
However, American spokesman Matt Miller said: "We're still working through the process to obtain slots [from the Japanese government]."
There is a limit to the number of foreign flights into Japan — four in the case of the United States — and US regulators are tasked to oversee that the level of access is controlled.
Delta discontinued its Seattle-Haneda service on September 30 after American filed a request with US regulators seeking to take over the flight rights to Haneda (see news, October 2014).
American had argued that it would provide a service that is "substantially superior to Delta's near-dormant Seattle to Haneda service".