If you check all previous Air Force (One,Two) aircrafts, they have all been 4-engine aircrafts, all the way back to Eisenhower and Truman.
and interestingly the Lockheed Jetstar owes itself to this .
Air Force requirements had nothing to do with it.
It was underpowered per the USAF and so
Hill Air Force Base Fact Sheet wrote:
Hill AFB Library Fact Sheet
Meanwhile, the Kennedy White House was looking for Presidential/VIP transport to augment the first 707s that were being used as Air Force One aircraft, and they contacted Lockheed asking if the JetStar could be re-configured as a four-engine aircraft. Lockheed turned to Pratt & Whitney Aircraft Engines about replacing the two French-built Orpheus engines on the original design with four Pratt engines and the plane was re-engineered to its current design, adding slipper tanks on the wings for extra fuel and range.
When you guys mentioned the Gulfstream, it made me remember back during the early 90's, I guess it must have been Clinton, was supposed to fly into SPI, but instead flew the 747 into STL and then flew the Gulfstream to SPI, thus being Air Force One.