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