What is the bubble on the upper deck of Air Force One?

That is not the airplane(s) which is normally used as Air Force One. It is a “Nightwatch” plane, formerly known as “Kneecap”. It is a Boeing 747 (E-4). The airplanes usually used as Air Force One are also Boeing 747s (VC-25s). read more

Since you ask “the bulge on the upper deck” you are not asking what is in the upper deck and since we all know you intended to refer to the 747 most commonly tagged as Air Force One the answer is the refueling receptor for inflight refueling. That is the bulge just forward and below the cockpit windows looking more like a broken nose. read more

Most windows on the upper deck of the VC-25s are plugged. On the left side, of the upper deck, is the White House communications suite. The right side is one of the Secret Service seating and lounging/resting areas. The crew rest area is also in the upper deck. The galleys are in the lower aft cargo compartment. read more