Pituffik Space Base, formerly Thule Air Base, is a United States Space Force base located on the northwest coast of Greenland in the Kingdom of Denmark under a defense agreement between Denmark and the United States. Denmark was a founding member of NATO in 1949 and the 1951 Greenland Defense Agreement allowed the United States to operate the base under a NATO framework. Under the agreement the Danish national flag must be side by side with the US national flag on the base.