iPadOS 8.4 (build 12H143) is an official Apple over-the-air update for the iPad Air (Cellular), released on 2015-06-30T15:51:13Z. The update package is 742.29 MB. This is a delta (partial) update that requires 8.0.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 998a0ca866cf857c0aa6a36842272e551a04f7b1.zip.