The US explored the concept of underground protection for aircrafts a long time ago and found it no better than above ground shelters. The EMP threat is overblown, and by you on this forum.
Runways can be repaired, yes. But does the PLAAF have the equivalent of the USAF Red Horse and Prime Beef engineering squadrons who specializes in runway repairs ?
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I have posted this example before, remember ?
The new philosophy is degradation over destruction. Do we want to destroy the actual warfighter -- aircraft -- instead of preventing it from take off ? Absolutely. But under certain tactical necessities, degradation of its ability to fight, as in runway denial, will be just as good. By the time the enemy repaired the runway, a crucial battle or vital asset may have been lost.