| * Click on CENTER for graphical tier information | ||
| ZME (ZME 1) | ||
| FIRST TIER | ZFW / ZHU / ZID / ZKC / ZTL | |
| SECOND TIER | ZAB / ZAU / ZDC / ZDV / ZJX / ZMA / ZMP / ZOB | |
| * Click on CENTER for graphical tier information | ||
| ZME (ZME 1) | ||
| FIRST TIER | ZFW / ZHU / ZID / ZKC / ZTL | |
| SECOND TIER | ZAB / ZAU / ZDC / ZDV / ZJX / ZMA / ZMP / ZOB | |