A-3B passing over the Mekong river

Some good info at Wikipedia

The Douglas A-3 Skywarrior was designed as a strategic bomber for the United States Navy, but its primary function for much of its later service life was as an electronic warfare platform, tactical air reconnaissance platform, and high capacity aerial refueling tanker. In these roles it was among the longest serving carrier-based aircraft in history, entering service in the mid-1950s and retired in 1991. Throughout its service, it was the heaviest operational aircraft to operate from aircraft carriers, earning its nickname, "The Whale."
https://en.wikipedia.org/wiki/Douglas_A-3_Skywarrior