iPadOS 11.4 (build 15F5071a) is an official Apple over-the-air update for the iPad Air (WiFi), released on 2018-05-07T17:10:50Z. The update package is 222.73 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: 552b525f990c4ff713ea878b6a5ecd97a2609067.zip.