What’s Your Guess About The Operating Altitude Of The B-21?

b-21 artist concept
Artist's rendering of the B-21A.
Credit: Northrop Grumman

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What’s your guess about the operating altitude of the B-21?

Defense Editor Steve Trimble responds: 

The U.S. Air Force disclosed here that future B-21 pilots are not expected to use low-altitude training routes. This statement correlates with a casual analysis of the released renderings of the B-21, which reveal a trailing edge optimized for high-altitude operations.

How high? The available evidence does not give us any specific clues, but some basic assumptions are possible. As Aviation Week noted on the eve of the B-21 contract award announcement in 2015, the answer is likely somewhere between the 50,000-ft. ceiling of the B-52 and the roughly 70,000-ft. operating altitude of the U-2.

“High altitude is one of the few ways to reduce the chance of visual detection—an observer in a fighter at 30,000-40,000 ft. is looking up against a dark sky, not outward against a backlit horizon,” Aviation Week reported in August 2015. “Even a usable 55,000-60,000-ft. cruise altitude (like the Royal Air Force’s Vulcan and Victor) could be an advantage.”

Steve Trimble

Steve covers military aviation, missiles and space for the Aviation Week Network, based in Washington DC.


Operating weight, wing area, engine power. Until all these things can be reliably guessed at, there is no answer.
My guess for operating altitude of the B-21 is well over 100 thousand feet in altitude!
Being high, when viewed from a mid altitude also means that you are being viewed in front of a very cold background, with very little IR blocking water vapor in between. The airplane's ambient relative warmth may be bright with the 4K ambient background.