Talk:Ace Combat Infinity/Update details/@comment-109.185.164.29-20150514163704/@comment-1824272-20150514163955

Each aircraft you own now has a certain "part slot upgrade points" threshold. If you sortie enough times with that aircraft, you'll earn those points, and once you earn enough points you'll get +1 part slot in each category.

The amount of points required to earn for the expansion depends on how many part slots your aircraft started with.