Question:
The Allies are flying a CAP mission to cover an airbase with heavy flak (irrelevant but the reason why this is happening). German fighters are in range to intercept. How is this handled?

Answer:

The CAP mission is a mission, so if the Axis want to intercept it, it is handled as any other interception. In this case, there is no escort for the mission force. The entire mission force consists of the CAP mission air units.

Let us assume that there are 12 Allied air units on CAP and the Axis intercept with six air units. Randomly select six of the CAP air units and pair each one off with a randomly selected interceptor. Since there is no escort, there is no screen to be attacked or bypassed. These six air to air combats are resolved. All of the surviving interceptors are returned to base once the combat is completed and the surviving CAP air units remain in the target hex with the other, unengaged CAP air units.

Note that the CAP air units, whether engaged or not, have not completed their mission yet and so none of them not affected by combat would be returned to base at this time. Let’s assume that the Axis achieved 1× K, 1× A and 1× R in the air to air combat and 3× no effect. Since 12 air units were part of the mission, we would end that interception with nine Allied air units on that CAP mission still over the target hex.

Note that just as a bomber doesn’t lose its mission ability by being intercepted (unless affected by the air to air combat), neither does a CAP air unit; it may defend itself against the interception, and still remain in the hex, and carry out its mission.

Source:
TEM 74