I get an error when trying to pull up any individual reservation from the My Bookings page. Although the search looks like it's going to a secure page (i.e., https), when I get the error message the Url is on a nonsecure page (http).

As a workaround I have found that if I manually insert the 's' (http --> https) in the address on that error page, the page reloads and displays the booking. I presume this results from some coding problem on Frontier's end.