Another option not yet mentioned, from U.S. military jargon, is in country, though this carries some contextual baggage. It's similar to in enemy territory and might be used by, for example, a carrier pilot while in an assigned combat or patrol area. It might contextually suggest to the reader that radio silence or strict concentration is important to the specific mission at hand. It would be less fitting if you want to suggest to the reader that this pilot's general, personal preference is simply to avoid chit-chat in the cockpit.
There's also the phrase sterile cockpit which just means a policy of avoiding distractions in the cockpit. This is a common phrase among pilots and would be used as in "She preferred to keep a sterile cockpit."
(Of course, these nuances will only matter to readers familiar with the jargon. There's always a balance to be struck between impressing those who know the jargon and alienating those who don't. Everyone understands "... while airborne" and pilots won't look at you funny for saying it.)