Subfolder site redirects

Hello all, I’m working on a WordPress site that has multiple subfolders. So in the htdocs folder, there is a folder for air, main, and ground which corresponds to..

http://americharter.com/air/
http://americharter.com/main
http://americharter.com/ground

Each subfolder operates as it’s own wordpress install. I need to add a subsite for stay, so I copied the air folder, renamed it to stay, modified to .htaccess file and uploaded via ftp. The site shows up just fine on the front-end live.. The issue is whenever I try to access wp-admin for the stay site, I get redirected back to the air login. Any ideas? Help is greatly appreciated.