KLM Royal Dutch Airlines was founded on October 7, 1919, which makes it the oldest airline still operating under its original name. It's based in Amstelveen, near Amsterdam, and is part of Air France-KLM. Its hub is Amsterdam Airport Schiphol, and it flies to around 160 destinations in some 70 countries, with many more reached through codeshares.
For US travelers, KLM flies nonstop from a number of US gateway cities to Amsterdam, where you can connect onward across Europe, Africa, the Middle East and Asia. KLM is a member of the SkyTeam alliance and has long partnered with Delta, so flights are often sold as codeshares and you can usually earn and use miles across the partner network.
KLM's loyalty program is Flying Blue, shared with Air France, where you earn Miles on flights and partner spend and can work up through status levels. Economy fares come in several types (such as Light, Standard and Flex) with different bag allowances and change rules, so check what's included before you book.