A pragmatic sequential mixed methods research methodology was used to examine commercial airline pilots' (N =156) types and frequencies of informal learning activities, perceptions of workplace informal learning, and opinions on how organizations should support workplace informal learning outside of the formal learning environment. This study found that pilots engage in various informal learning activities to learn something new for work. Comparison of informal learning activities pilots use to learn something new for work and preparing for regulatory compliance training showed significant changes in frequency of engagement of informal learning activities. Two environmental factors lack of time and proximity to colleagues were found to inhibit pilots from engaging in informal learning activities. Five personal characteristics were found to motivate pilot's informal learning activities: initiative, self-efficacy, love of learning, interest in profession, and professionalism. Interview findings (n = 14) found that informal learning is an integral part of workplace learning. Findings on support of informal learning outside of the organization showed pilot's access to technical information is limited. Access to additional information emerged as one method organizations should employ to support workplace informal learning. These findings have implications for future informal learning research in professions that practice in high reliability domains. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]