Northrop Grumman B-2 Spirit - Wikipedia
https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit
The Northrop (later Northrop Grumman) B-2 Spirit, also known as the Stealth Bomber, is an … Though designed originally as primarily a nuclear bomber, the B-2 was first ….. It is speculated to have an upward-facing light sensor which alerts the pilot to increase or reduce altitude to match the changing illuminance of the sky.
First flight: 17 July 1989