iOS 11.3 (build 15E5216a) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-03-16T17:05:20Z. The update package is 54.01 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: 192e2aebada101ccea4d1f20c91756c5c955ca2c.zip.