Complex sentence: Although not officially acknowledged by the U.S. Air Force until 1988, the F-117 became operational in 1983 and the Wiesbaden airbase would "go dark", turning off all airfield and perimeter lights, whenever "stealth" flights were landing or taking off.
Split into simpler sentences: Although not officially acknowledged by the U.S. Air Force until 1988, the F-117 became operational in 1983. The Wiesbaden airbase would "go dark", turning off all airfield and perimeter lights, whenever "stealth" flights were landing or taking off.