Behind the scenes, they're very likely using metric. For press releases and such, however, it's worth remembering that the primary audience is the American public, and said public - for better or worse - uses those antiquated units.
> The spacecraft encountered Mars on a trajectory that brought it too close to the planet, and it was either destroyed in the atmosphere or escaped the planet's vicinity and entered an orbit around the sun.[2] An investigation attributed the failure to a measurement mismatch between two software systems: metric units by NASA and non-metric ("English") units by spacecraft builder Lockheed Martin.
https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...
This isn't true at all, lol. Aerospace in the US has used 'english' measurement from the start. My take on the matter is that all units are arbitrarily defined and flip flopping the units that we already use is a silly idea of progress.
The strength of the metric system is not on the particular dimension of their definition, but lies in the use of a decimal system. That is what makes it superior to the old imperial system and why the scientific community in the US uses it. Using a single base system for all your numbers, and the same base system as the one used in your numbering systems is the only way you can do complex computations without resorting to many magic numbers.