iPadOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPad 2 (Mid 2012), released on 2016-03-31T16:51:13Z. The update package is 825.8 MB. This is a delta (partial) update that requires 8.0.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 799640ec620fe0bf10a95ec332854f9017d0e8c2.zip.