How do I enable/disable automatic check-in for future flights (iOS only)?

As you complete the automatic check-in steps (on the "Boarding Pass" widget for the upcoming flight), enable/disable the "Auto check-in for each flight" option before you click "Save".

If you have already checked in, click on Status > then go through all the screens, and on the page with the "Cancel" button turn off "Auto check-in for every flight",

and click the "back" button in the upper left corner.