Interceptors is an optional rule that is described in the official FAQs for V3 and V4 that would be appreciated by the community.
Ideally, it would be an optional rule for V3 and V4.
Official description rom the faq:
Fighter Escorts and Interceptors
Fighters can participate in strategic bombing raids. Attacking fighters may escort and protect the bombers, and they
can originate from any territory, range permitting. Any or all defending fighters based in a territory that is strategically
bombed can participate in the defense of the industrial complex. The number of fighters that will defend is decided
after the attacker's Combat Movement phase is completed and before the Combat phase begins.
After antiaircraft fire is resolved against the attacking air units, if there are any defending fighters an air battle occurs
between the attacking and defending air units. This combat is resolved in the same way as a normal combat, with a
few exceptions. The fighters have an attack value of 1 (2 if the attacker has the Jet Power research breakthrough)
and a defense value of 2, and the bombers have no attack value. In addition, the combat lasts for only one round.
After the battle, any surviving bombers proceed to carry out the raid as normal.
Fighters participating as either an escort or a defender cannot participate in other battles during that turn. Defending
interceptors must return to their original territory. If that territory is captured, the fighters may move one space to land
in a friendly territory or on a friendly aircraft carrier. This movement occurs after all of the attacker's combats have
been resolved and before the attacker's Noncombat Move phase begins. If no such landing space is available, the
fighters are lost.