iOS 11.3 (build 15E5211a) is an official Apple over-the-air update for the iPhone 6, released on 2018-03-12T17:05:47Z. The update package is 228.64 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: b6bcd91043a489c17750e4d51d6f9dffe216d3d1.zip.