iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad mini 4 (Cellular), released on 2018-04-24T17:07:24Z. The update package is 615.08 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: 49f749e20f7d0f350de200242865a2a90dc2e0bc.zip.