Note: A zero star unit will usually fail to completely destroy a crewed weapon, simply because both bombs will be that far off target!
CAS (Close Air Support)
Airplanes can be used to directly support the efforts of ground troops by supressing and weakening nearby enemy units. CAS should be employed whenever necessary! For example, low quality infantry could very well attempt a breach against elite infantry, when supported by a well timed (and well aimed) bombing run.
Airplanes can be used independently of ground forces to preemptively destroy high value or dangerous (17-pdr (UK), M5 Gun 76mm) or otherwise impossible-to-reach targets well ahead of own troops and behind enemy lines! Provided they are reconnoitered ;-)
Cost vs Usefulness
Without requiring repairs, a bomber can be called in only three times in about 10 minutes. And bombers are especially costly units. With this in mind it must be weighted carefully whether to use them as soon as they become available again to do as much damage as possible with them or the wait untill there is a call for a CAS run.
A mainstay of the Luftwaffe's arsenal, the Junkers Ju 88 was a twin-engined multirole combat aircraft introduced in 1939. The design suffered from numberous technical problems in its early years, primarily as a result of feature creep and constant piling of new features onto the plane. Most of the issues were rectified by 1941, and by summer of 1941, the Ju 88 became the durable war horse it's remembered as, evenetually becoming one of the most important aircraft designs of Nazi war machine, serving as a bomber, dive, bomber, night fighter, torpedo bomber, recon plane, heavy fighter, and even a flying bomb.
Nearly 16,000 air frames were built in dozens of variants, but the basic structure of the aircraft remained unchanged.