Would any jet flying boats enter service during the 1950s in this timeline?
Short answerPossibly; slower airfield expansion preserves their infrastructure advantage, making a Saunders-Roe-like jet flying boat more practical.
NotesAn aircraft resembling the Saunders-Roe Princess could enter service in this timeline. World War II historically built an enormous network of conventional airfields, reducing one of the flying boat's central infrastructure advantages. Without that emergency program, land bases spread more slowly and a water-based long-range aircraft remains attractive. Jet propulsion could therefore extend the flying boat's life even if the resulting machines still look unconventional.