The Boeing NKC-135A Airborne Laser Lab in the air. I recently posted a photo from the US Air Force Museum of "Hump" at the Aircraft Park. Found this US Air Force photo of it in the air.
While the KC-135A was usually used for in-flight refueling, the Airborne Laser Lab was a modified version used for flight testing. Similar to the commercial Boeing 707, the slightly smaller KC-135 was designed to military specifications and operated at high gross weights. The KC-135A's initial flight occurred on Aug. 31, 1956, and the USAF accepted its first one on Jan. 31, 1957. By 1966, 732 KC-135As had been built, and the aircraft had become the USAF's standard tanker. It was also used for transporting cargo or personnel and by 1970 was serving in other roles, including reconnaissance, electronic intelligence and project testing.
Nosey & Hump at the US Air Force Museum
Canadian Airline Blog