Originally Posted by
hairpeace
HKG-NRT-DEL-NRT-SIN-SYD-AKL-SYD-JFK-LAX-SJO-LAX-SAL-LAX-LHR-MCT-LHR-CPT-JNB-HKG
67756 miles
HKG-NRT-DEL-NRT-SIN-SYD-AKL-SYD-JFK-LAX-DFW-ANC-DFW-PHX-LHR-MCT-LHR-CPT-JNB-HKG
65677 miles
Would like suggestions on maximising the mileage. Trips will be in F.
Thanks!

Here's a variant with 20 segments and 69,586 mi per GCM -
HKG-NRT-DEL-NRT-SIN-SYD-AKL-SYD-JFK-YVR-DFW-ANC-DFW-MIA-PHX-LHR-MCT-LHR-MRU-JNB-HKG
If you need to get to CPT or LAX those flights are cheap from JNB and PHX respectively. Uses the CX JFK-YVR flight and LHR-MRU. Note YVR-DFW doesn't have F.
Is there F on NRT-DEL?