Alamillo missed 10 calls in 2012. For the first three missed calls, Alamillo received additional training instead of discipline. For the next four missed calls, he received a 10-day suspension and a 20-day suspension. A supervisor advised Alamillo to obtain a pager or a landline number where BNSF could contact him to ensure that he would not miss another call. He did not do so, or take any other action to make sure he would not miss another call. Alamillo missed three more calls, the last being on June 16, 2012, and BNSF decided to impose discipline. Alamillo switched to a regular schedule, and was able to wake up on time and appear at work on time every day. On July 29, 2012, Alamillo was diagnosed with obstructive sleep apnea (“OSA”).