iOS 9.9.11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone 6, released on 2018-04-24T17:10:19Z. The update package is 1.48 GB. This is a delta (partial) update that requires 9.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8af968d8921e79e5a5400a7717dd1ec8a6357a6f.zip.