| 1 | IPL | Air Charter Services (Pty) Ltd, South Africa | Callsign: Imlala Air, | ZA | AVCODES |
| 2 | IPL | Airpull Aviation | | | ICAO1 |
| 3 | IPLC | INERGY PROPANE LLC | | | SCAC4 |
| 4 | IPLN | INDEPENDENT TRANSPORTATION LOGISTIC | | | SCAC4 |
| 5 | IPLX | Illinois Power Co. | added 1/1965; 7/1965-1/1980; eliminated 4/1989; 1/1994-7/2005 (not listed) | | NAKINA |
| 6 | IPLX | Illinois Power Co. | added 1/65; 7/65-1/80; eliminated 4/89; 1/94-7/2000 | | NRHS |
| 7 | IPLX | ILLINOIS POWER CO. | | | PWRC |
| 8 | IPLX | Illinois Power | | | RSRV |
