No Canopy: Max speed lock (if this is possible)

Bird Cage: Unlocks speeds over a certain amount (if this is possible). Increases cost.

Malcolm Hood: Increases defense (I see you coming!); increases agility [slightly] (I can more quickly anticipate, see, and counter your attacks). Increases cost.

Bubble Canopy: Increases defense, agility and attack. Increases cost a lot.

Pressurized Cabin: Comes later. Increases cost quite a bit. Main advantage is high altitude flying which increases attack ability. Since I'm not sure how the air combat formula works, I do not know the best numbers to manipulate to mimic the advantages of high-altitude flying.

Fighter Canopy Tech Line

Assumed Starting Tech: No Canopy / Open Cockpit (or small windscreen only)

Tech 1 "Bird Cage" (e.g. Bf 109) - Flat glass sections held in position by a metal frame and muntins. Rear view is blocked. The frame causes blind spots.

Tech 2 "Malcolm Hood" (e.g. Spitfire) - Expanding the bird cage concept but bulging the glass outward and adding flush-mounted recessed glass panels behind the openable canopy giving a better view to the rear.

Tech 3 "Bubble Canopy" - A single piece of plexiglass constructed without bracing that allows a full 360 degree view.