The two carriers have fought for months over the rights to fly into Haneda Airport in Tokyo. It's much closer to Central Tokyo than Narita is and business travelers prefer it.
First, American complained to the U.S. Transportation Department that Delta had allowed a route between Seattle and Haneda to go dormant and asked the Transportation Department to revoke Delta’s right to fly it.
The government allowed Delta to keep the route provided it flew every day. Delta called that ruling "Draconian" and ceded the Seattle route to Haneda back. American then got approval to fly out of Los Angeles to Haneda.
Now Delta claims American did not start the route within 60 days, something the government required American to do, and has complained to the Transportation Department. American said it will respond to the Transportation Department on Delta's claims. American's spokeman, Matt Miller, said “We’re still working through the process to obtain slots”