Congress can delegate decisions to expert bodies, and often does. But Congress is also quite comfortable simply legislating a solution, which may be ill-informed or with ulterior intent.

Speaking of planes, Congress took a direct role in the design specifications of the F-35 to the detriment of that program. Notably, they required a common airframe that could support VTOL, despite objections from the Army, Navy, and Air Force (the USMC wanted it and lobbied for it). This greatly added to the complexity and cost of the program.