In a former life (Marines), aircrew were issued 38’s, in my squadron when we went on cruise one could bring there own sidearm if they desired. I recall one guy brought a 357 and another an Uzi.
Not sure what is standard issue now.
I started with the .38 (1980), then the .45, and before I got out (2001) Aircrews were using the Beretta, 9mm.