iPadOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPad Air 2 (Cellular), released on 2017-12-13T18:08:35Z. The update package is 356 MB. This is a delta (partial) update that requires 11.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ec45fa99733491a2386b74f00e491c29d00cd6de.zip.