iOS 11.3 (build 15E5216a) is an official Apple over-the-air update for the iPhone 6, released on 2018-03-16T17:05:19Z. The update package is 53.72 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: 7208edbd87feb135b59c056d7d522062b55c424d.zip.