The Fly Delta app for Windows Phone has been updated, but there still seems to be issues with logging in for many consumers. These problems were raised by users prior to this release being published, so one would expect the update to contain the necessary improvements, correct? The latest release includes "Bug fixes & performance enhancements" and no, we're not trolling you.
The app listing confirms that the team behind the Fly Delta Windows Phone app has indeed applied a number of bug fixes and performance enhancements, which will be noticeable to those who can actually get the app to work. It may be the case that the team has merely made a mistake and has somehow submitted the wrong version, or has overlooked some of the fundamental problems with the experience.
You can download Fly Delta for free from the Windows Phone Store. Let us know in the comments if you're having trouble with Fly Delta.