Not anything satisfying. I can breakout of the iFrame to the F5 login prompt, but that defeats the purpose of the iFrame. F5 doesn't do a pop-up prompt like Microsoft, so that's not helpful. The ultimate solution was that application administrator redirected the user to a normal page behind the F5, then the F5 served up the regular login page, and afterwards the application administrator would redirect the user back to the original page with iFrame. Since the user already had a cached session the iFrame loaded no problem. Not the ideal solution, but it served it's purpose.