KLM is a member of the SkyTeam airline alliance.
KLM has codeshare agreements with a number of airlines. This means that KLM may offer connections under a KLM flight number, but that the flight may be operated by the codeshare partner. This enables KLM to offer a worldwide network.
KLM, Air France, Delta and Alitalia also have a joint-venture.
In 1989 KLM acquired a 19.3% interest in Northwest Airlines. In 1991 both airlines began operating codeshare flights on the North Atlantic route. The open-sky treaty signed by the Netherlands and the USA in 1992, and the anti-trust immunity granted to KLM and Northwest in 1993, enabled the airlines to operationally evolve a joint venture. The joint venture agreement was signed in 1997.
A year later KLM and Northwest integrated their sales activities, with Northwest taking responsibility for sales in North America and KLM in Europe. In 2009 Northwest and Delta Air Lines merged and the Northwest brand disappeared. Delta is now an important partner in the joint-venture with AIR FRANCE KLM.