In August, 1955, Boeing test pilot Tex Johnston performed a now legendary barrel roll of the Model 367-80 as part of that year’s Seafair festival on Lake Washington. This photo was taken by co-pilot Jim Gannett.
His now famous quote is
One test is worth a 1,000 expert opinions
When asked "why use agile methods for developing software in any domain?" the answer is "measuring physical percent complete through the evidence of working product is worth a 1,000 page of specifications.
This is standard agile language, but in the domain of federal government procurement and development, those pesky specifications, contract clauses, organizaiton structures, and demanding Generals with stars on their shoulders aren't going to let radical developers loose on their programs.
But at some level in the program, usually at the Work Package and sometimes above on the Rolling Wave, things like Scrum are applied and we just don't tell anyone about it.
In exactly the same way Tex Johnson didn't tell anybody he was going to roll the Dash-80 (early Boeing 707 model) in front of 100,000 people. He knew it would work. It was a nice 1G outer loop roll, where all the people on the aircraft experienced no change since the 1G held them in their seats.