msfsx .air files report as corrupted

Hi, I tried to run msfs x recently and the engine sound when flying any plane was silent when flying from the left seat but when taking a spot view or outside view the sound was there. Upon looking at the file structure I found that the .air file foo every plane was reported as corrupted and that I should get new files from original author. How do I do that when Aces studio has long gone out of business. How do I get the file for the Cessna 172. 208, Extra sport plane, etc. Anybody able to help me out here?
Regards, Wayne

What did you do to corrupt the files? Did you install any new addons or software? Also, how do you know they are corrupted?

If it's only the default aircraft then you could possibly re-install FSX. Is this the disc version or the Steam Edition?