The B-17F had a single piece nose installed.
Propellers were slightly larger. Engine cowling was reshaped. Oil tanks were self sealing. Wings and undercarriage strengthened to allow for larger bomb loads. Link between Norden bombsight and autopilot installed. "Tokyo tank" were installed in outer wings to allow for an additional 1,000 mile / 1,610 km range. Could carry 1,000 lb / 454 kg of bombs under wings. Late in production Bendix chin turret added.