United has the strongest hub network in the industry, and its trans-Pacific routes are the envy of its rivals.
Paul, also draws significant revenue from its trans-Pacific routes.
American has not yet taken delivery of the planes it plans to use on the trans-Pacific route, the department said.
It entered service in 1939 flying trans-Pacific routes.
On competitive trans-Atlantic and trans-Pacific routes, this has apparently proved an impediment to action by individual airlines.
During the 1970s, the company continued to build new vessels capable of container transport, but pulled back from worldwide freight service to purely trans-Pacific routes only.
On days when the headwinds at lower latitudes are particularly strong, capacity is sometimes 60 or 70 passengers fewer on the trans-Pacific route.
Nevertheless, American carriers continue to dominate the trans-Pacific route, accounting for 69 percent of the traffic between the two countries.
Toronto is the airline's main hub, and trans-Pacific routes are among its most profitable.
The 747-300s replaced the 747-200s on all trans-pacific routes as well as the prime European destinations.
