If you liked to get technical about it look here: https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191
We used nitrogen in the C-5 cargo aircraft because it is dry (won't freeze moisture at altitude) and hold pressure better, yet each time the aircraft returns we check and service nitrogen to inflate 28 tires to proper pressure.
Using nitrogen doesn't mean you don't have to check your tire pressures and even in the winter you have to add nitrogen because the pressure will drop due to cold temps.
Air is 78% nitrogen, 21% oxygen, and 1% miscellaneous gases.