The answer of course is that it depends. Inter-aircrew communication varied by nation and the date of the war. Generally speaking, communication was through an internal intercom system that piped into headphones on the flight helmet. The Western Allies tended to have the most reliable radio systems for this, but many good commanders tried to minimize the chatter.

This was necessary given the spread out nature of most Allied bombers. Turret gunners often had separate duties. For instance, the top turret gunner on B-17s was the plane's flight engineer (assisting the aircraft's operations) and was the senior NCO for the aircrew. The tail gunner was an observer for the plane and had to keep tabs on the formation. Even though the ball turret gunner was shut inside a plexiglass globe, he was to assist the navigator (also responsible for the chin guns) with local landmarks. Waist gunners acted as a jack of all trades to aid the other aircrew. this could mean repairing battle damage or treating the wounded.

As alluded to above, many WWII bombers had a different set up. German bomber design philosophy stressed locating all the crew into the front cockpit area. This meant conditions were cramped, but communication was quite easy. Like the Anglo-Americans, gunners had double duty managing the radio, bombardiers and navigators. The cramped cockpit was a mixed blessing as a hit could disable more than one aircrew member. One of the grim advantages of the large British and American bombers was that their large design meant that if an aircrew member was wounded and died, the aircrew might not see him and could better carry on with the mission. German bomber crew did not have this luxury.

The Japanese aircrew had a terrible war. Japanese radios were often quite poor and interaircrew communication was rudimentary. Added to this, the mountings and caliber of weapons on Japanese aircraft was insufficient to adequately defend the aircraft from Allied fighters. Some Japanese bomber turrets were manually driven by bicycle pedals, a tiring prospect at high altitude in an unpressurized aircraft. Although the Japanese adapted heavier caliber weapons as the conflict drew on, it was too little too late.