“I think the case is very strong that masks don’t add much, if anything, in the air cabin environment. It is very safe and very high quality compared to any other indoor setting,” said Southwest CEO Gary Kelly.

“I concur. An aircraft is the safest place you can be. It’s true of all of our aircraft — they all have the same HEPA filters and air flow,” said American Airlines CEO Doug Parker.

https://www.cnn.com/2021/12/15/business/airline-ceos-question-masks-on-plane-rule/index.html

They are absolutely right. A University of Waterloo study earlier this year found even the best performing type 95 masks prevent aerosol concentrations less effectively than even moderate ventilation of two air changes per hour. Commercial aircraft typically provide 20 to 30 air changes per hour.