@jimrpa
I certainly don't think Delta needed to create the iOS app given how well (relatively) mobile.delta.com works on the iPhone. I've been using it to get all my needs done while mobile with hardly a need to open up my computer. Especially given Apple's approval process, one can expect more resources to be spent supporting an iOS app rather than a iOS HTML solution like Gmail.

HOWEVER - and this is a big however, I think Delta really wants to offer it's iPhone users the ability to do paperless check-in in more locations. See Paperless Mobile Checkin on Delta's Blog.

The rest of the stuff is run-of-the-mill and doesn't require an app, but this particular feature appeals to me.

Not to mention the slight benefits of improved UI, "free" advertising among the tech journalists, and keeping-up-with-the-Jones' attitude in the App Store.

Marketing Departments always beat IT Departments in the executive offices.