Funding for this research was provided by:
Federal Aviation Administration (13-C-AJFE-UPENN-004)
Received: 1 April 2019
Accepted: 13 November 2019
First Online: 5 December 2019
Ethics approval and consent to participate
: The study was reviewed and approved by the University of Pennsylvania Institutional Review Board (Protocol number 823726). Regarding responses to the postal survey, the IRB reviewed and approved a waiver of written documentation of consent as per HHS 45 CFR 46.117(c)(2). Informed written consent was obtained for participation in the field study.
: Not applicable.
: The authors declare that they have no competing interests.