The NASA AD-1 was first prototyped in 1979. Unlike most other planes, its wings can be adjusted along the horizontal axis.
Look closely at the photo. You will notice that the wings are splayed at a 60-degree angle to the body of the plane.
An aeronautical engineer named Robert T. Jones came up with the idea first. An oblique wing, he thought, might be able to double an aircraft's fuel efficiency.
Oblique wings were effective, but made flying much more technically complicated. The idea was eventually shelved.