Re SIN-LHR, BA, QF and others from various parts of Europe have avoided Afghanistan for many years in both directions. Most Asian airlines and Aeroflot did fly over the top but all have ceased.
As to range, any reports of a certain S E Asian airline (not SIA) landing in London with nearly empty tanks is to do with economics, not range. On a journey back from SIN-LHR in 1997, on QANTAS, we routed over India, near Bombay and we were planned over Saudia Arabia, Jordan/Syria and Turkey.
There was some almighty cock up as the crew told us we were denied Saudi entry as planned due to Hadj traffic conflictions and we headed North East over the Gulf, into Iranian airspace from where Turkey refused us entry, so we ended up dog legging over Armenia, west along the Black Sea and over Romania. We left SIN before BA and SIA and landed well after them, journey time 14 hours 24 mins.
On the other topic raised here, re the 747 and the USAF transport, I assume this was in dense cloud, at cruise level?
The C141 cruises at Mach.74 to Mach.80, the C5 at Mach .76 to Mach .825. The 747 cruises at Mach .84.
If on the same track, the 747 would overtake both types and any wake turbulence would be apparent long before even a 150 feet encounter.
In normal circumstance, at the rate of overtaking, the aircraft would have been visible for a long period before any turbulence. In that neck of the woods the sky is normally clear at altitude. Both the C141 and C5 look large from behind and tend to leave large contrails from the engines and/or visible wake vortices and, these can be seen at all times except on the very darkest night.
C141 and C5 traffic, even in proximity to war zones, still monitors civilian frequencies and doesn't occupy civil air lanes without ATC control. It also monitors the civilian "guard" VHF frequency in HF controlled areas.
Now back to the "15 ft" bit. A near miss may have happened during the Gulf War but not as stated, not that close and not due to the fact a conflict was taking place.