Also, since you work in the super secret airline business that you can't discuss, I thought you might like this study. Even at simulated 5k feet at 17.61% oxygen (rather than sea level 21%), masks caused no adverse effects.https://commons.erau.edu/cgi/viewcontent.cgi?article=2554&context=publication
The COVID-19 pandemic has required people to take new measures to mitigate the spread of the communicable
virus. Guidelines from health organizations, government offices, and universities have been disseminated.
Adherence to these guidelines cannot be more critical for flight training. This study explored the effects face masks
had on CO2, heart rate, respiration rate, and oxygen saturation while wearing a face mask at an oxygen level
simulated to 5,000 feet. Thirty-two instructor pilots (IP) volunteered to participate in the study. IPs spent 90 minutes
in a normobaric chamber while wearing a cloth face mask or a paper face mask. Participants were measured before
entering the chamber, at the 15-minute mark, at the 45-minute mark, at the 90-minute mark, and after exiting the
chamber where they briefly removed their mask for a final measurement. No differences were found between type
of face mask. Wearing face masks did not present any potential health or safety issues for the IPs. However, IPs did
report moderate dislikes (e.g., comfort, issues with fatigue, restriction of movement) of wearing face masks.
Although face masks may be a nuisance, it does not appear to create any health or safety issues at a simulated
altitude of 5,000 feet