iPadOS 8.4 (build 12H143) is an official Apple over-the-air update for the iPad Air (WiFi), released on 2015-06-30T15:51:12Z. The update package is 711.15 MB. This is a delta (partial) update that requires 8.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: cf5742b2e0e24b876cc30bf003865d0e77947767.zip.