iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad Air (Cellular), released on 2018-04-24T17:05:18Z. The update package is 577.84 MB. This is a delta (partial) update that requires 11.2.6 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 88bc81b47fce371a1add6cdc3c9f0f54f143c060.zip.