Plans for the ROC military to flee eastwards to the eastern coastline for regrouping and reorganizing a counterattack should be anticipated, in my opinion. For that, the PLA would have to saturate the military installations along the eastern half of Taiwan with guided missiles and guided bombs first, mainly through shipborne missile and land and carrier-based air attacks.
One thing to note is that there are two major ROCAF air bases located on Taiwan's east coast, namely Chiashan Air Base in Hualien and Chihhang Air Base in Taitung - both of which have extensive underground hangars being built underneath the mountains. Capable of housing 200 and 80 aircrafts respectively, they are meant to shield those sheltered planes from China's air and missile strikes from the mainland using the Taiwanese mountain ranges as cover.
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Although, one thing that I am very thankful for is that the ROCAF does not operate any VTOL or SVTOL fighters, which meant that they are fully dependent on runways. And we all know that runways can be cratered easily with anti-runway munitions in the PLA's military arsenal.
Back to the point - Since destroying individual planes underground hangars in Hualien and Taitung using conventional air and missile strikes are practically impossible, I do envision that the PLAN and PLAAF would use low-altitude, ground-hugging missiles from the east and south that could struck and collapse all the tunnel entrances and exits into those underground hangars.
MOAB/FOAB-like bombs are also useful to shake the terrain hard enough so as to trigger collapses of those tunnel entrances, although air supremacy must be obtained/total surprise must be achieved, as MOAB/FOAB-like bombs shown below (by the PLAAF in 2019) could only be carried by bombers that are vulnerable to enemy aircraft and air defenses.
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Here's a brief read regarding China's underground hangars by Business Insider dated way back in 2012:
Collapsing those tunnel entrances would definitely help to trap any ROCAF planes still inside those underground hangars for considerable periods of time, alongside cratering the runways and taxiways of those airbases. This would aid significantly in PLAAF's work in clearing up Taiwan and enforcing China's grip over the island as quickly as possible.