iOS 11.3 (build 15E5201e) is an official Apple over-the-air update for the iPhone 6, released on 2018-03-05T18:14:01Z. The update package is 319.97 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: 575e23afd843a81a647c3bc6f6cdbf481be30cdc.zip.