iPadOS 11.4 (build 15F5037c) is an official Apple over-the-air update for the iPad Air (China), released on 2018-04-02T17:06:24Z. The update package is 225.18 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 0023dc35cb06a6dbf8990ec1fdd379a4912d771f.zip.