iPadOS 9.9.11.2.1 (build 15C153) is an official Apple over-the-air update for the iPad Air 2 (Cellular), released on 2017-12-13T18:08:19Z. The update package is 1.35 GB. This is a delta (partial) update that requires 9.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7293447c50793f931749372b634f41ba51b31faa.zip.