iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone 6+, released on 2016-03-31T16:55:17Z. The update package is 303.44 MB. This is a delta (partial) update that requires 9.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c4d23733a03535cb7b7cec6e1c3df827179c3baa.zip.