iPadOS 11.4 (build 15F5071a) is an official Apple over-the-air update for the iPad Air 2 (WiFi), released on 2018-05-07T17:11:10Z. The update package is 198.55 MB. This is a delta (partial) update that requires 11.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6f8d161d0b4e5752c606564cb20c03eb285230fc.zip.