iPadOS 12.1.3 (build 16D5032a) is an official Apple over-the-air update for the iPad Air (Cellular), released on 2018-12-19T18:06:33Z. The update package is 201.2 MB. This is a delta (partial) update that requires 12.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 547ab982ad62e453a4fe4f3e8eacb0b805f28995.zip.