Designated RF-4X, this version of the Phantom was now capable of cruising at Mach 2.4 at high altitude with burst capability to Mach 3.2. This level of performance now began to alarm the US State Department- up to this point Mach 3+ aircraft were the sole purview of the United States and Soviet Union and in some diplomatic circles there were concerns about the Israelis integrating nuclear weapons delivery with the RF-4X.
"In the vast library of socialist books, there’s not a single volume on how to create wealth, only how to take and “redistribute” it.” - David Horowitz
Interesting. I was always told by our F4 drivers the air frame was mach limited. The J79s didn't care and would keep spooling until the jet came apart.