iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad Pro 12.9-inch (Cellular), released on 2018-04-24T17:08:54Z. The update package is 31.82 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d51850ae36b91b34d0e203a8bce2f57f09a65112.zip.