The Boeing Model 853-21 Quiet Bird was a US Army reconnaissance plane study developed by Boeing in the early 1960s from their Model 831.
[1] It was an early example of stealth technology, especially electromagnetic low-observability.
[2] Development of the Model 853-21 began in 1962 at Boeing Wichita, only a 1/2 scale prototype was produced which never flew, but tests showed that it had a very low radar cross-section (stealth aircraft).
[1] Data from Boeing[1]General characteristics Performance
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