iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone 6, released on 2018-03-29T17:12:29Z. The update package is 774.34 MB. This is a delta (partial) update that requires 11.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 981b307cd8e5ca62d68f23b86198d569e88e40db.zip.