Wirelessly posted (iPhone: Mozilla/5.0 (iPad; CPU OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9B176 Safari/7534.48.3)
I buy all my tickets as one ways, and never had an issue since 2003. I often book tickets day of departure or a day or two ahead and also don't have issues. Not sure how/if that'd affect me being selected for pre check or not...