The United States’ Department of Transport (DoT) has allowed Vietnam Airlines and Delta Air Lines to widen their codeshare cooperation.

The approval comes after both carriers first inked an agreement last August with the intent of upgrading their relationship.

The cooperation, expected to take effect this month, will see both carriers put each other’s code on their respective flights, whether within Vietnam or the US, or from Vietnam and/or the US to other points in the network.

From this month, Delta will be able to sell tickets for Vietnam Airlines-operated flights between Hanoi and Tokyo, for passengers connecting onward to the US.

Furthermore, Vietnam Airlines’ code can be placed on flights operated by Delta’s regional affiliates, which include SkyWest Airlines, Compass Airlines, as well as Republic Airlines.

The DoT approval follows Vietnam’s attainment of Category 1 status from the US Federal Aviation Administration, which allows Vietnamese carriers to offer services to the USA and carry the code of USA-based airlines.

It builds on a 2010 agreement both SkyTeam members signed, which allows Vietnam Airlines to sell onward connections aboard Delta from Tokyo Narita and Frankfurt.