iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone 6, released on 2016-03-31T16:55:21Z. The update package is 369.94 MB. This is a delta (partial) update that requires 9.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d527f82332393f0b02886e8f8e73151707679fc0.zip.