Taiwan is pouring billions into hardening its underground air bases, a sign the island is preparing for the possibility that its air fleet has to survive a Chinese missile strike.

• The Chiashan cave complex in Hualien, built into the mountains to shelter fighter jets, has run on the same systems for over 30 years and is wearing out.
• The air force has budgeted NT$3.6 billion through 2031 to overhaul ten systems there, including power, ventilation, emergency generators, fire safety and blast doors.
• The upgrade adds protection against chemical, biological, nuclear and electromagnetic pulse attacks — the kind of threats expected in a real war.
• Parts are getting hard to find because the original makers stopped production, a common problem with aging military gear.
• A separate NT$6.9 billion is going toward 26 new hardened aircraft shelters at Chiashan and the Shihzishan base in Taitung, plus NT$940 million to rebuild the main runway at Ching Chuan Kang.

Outlook: The spending plans go to Taiwan's legislature as part of the 2027 defense budget, and the work would stretch to the end of the decade.