Flight attendants currently use Nokia Lumia 1520 phablets, which will be replaced by the iPhone 7 Plus as an in-flight point of sale and customer service tool.
Delta pilots are currently using Surface tablets in the flight deck as an electronic flight bag, with those tablets set to be replaced with the iPad Pro.
Though Delta is transitioning away from Microsoft products as it adopts the iPhone and iPad, the email says Delta "continues to maintain a strong and positive partnership with Microsoft." Some of the apps used on the iPhone 7 Plus are powered by Microsoft Dynamics.
The hardware change is pard of an "overall Delta hardware refresh" to standardize on a 10.5-inch form factor, a Delta spokesperson said.
iPhones and iPads will begin rolling out to flight attendants and pilots next year.