MD-82
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Troubleshooting
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Procedure; Human Factors
When loading the flight plan. We put in the fix KA12Q instead of KA21Q. We reviewed the plan and mileage and did not catch the error. I said will double check to be sure I don't transpose numbers again. Because the two fix's are about 108 from our last waypoint the mileage is about right. They need to change the fix name. It easy to swap the number and they are too close in mileage to show something is wrong with total mileage.
MD80 Captain reports inadvertently entering the waypoint KA21Q as KA12Q during preflight causing a track deviation. The route mileage increase caused by this error was reportedly not significant enough to be detected during checking.