iPadOS 11.4 (build 15F5071a) is an official Apple over-the-air update for the iPad Air (China), released on 2018-05-07T17:10:53Z. The update package is 222.49 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: ed807f1bdcbed5704d28b57f06a41f9328ec5d7c.zip.