iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad 5 (Cellular), released on 2018-04-24T17:08:10Z. The update package is 624.25 MB. This is a delta (partial) update that requires 11.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ace2edc93d6ee9f67f5119f052b39a62ae92264c.zip.