What is the quickest flight time from Calgary to Memphis?

A random search for flights from Calgary (YYC) to Memphis (MEM) shows: OPTION 1: 5hr 38min via Denver (DEN)

YYC - DEN United Airlines Flt 5925 Dep 08:00am 17Oct,Sat

DEN - MEM United Airlines Flt 6590 Dep 11:20am 17Oct,Sat

Flight Duration: 4hr 45min; Layover Time: 0hr 53min; Total Trip Time: 5hr 38min OPTION 2: 6hr 28min via Minneapolis (MSP)

YYC - MSP Northwest Airlines Flt 1510 Dep 01:55pm 17Oct,Sat

MSP - MEM Northwest Airlines Flt 3558 Dep 07:10pm 17Oct,Sat

Flight Duration: 5hr 02min; Layover Time: 1hr 26min; Total Trip Time: 6hr 28min OPTION 3: 6hr 30min via Houston Intercon (IAH)

YYC - IAH Continental Airlines Flt 0635 Dep 07:00am 17Oct,Sat

IAH - MEM Continental Airlines Flt 2998 Dep 01:00pm 17Oct,Sat

Flight Duration: 5hr 33min; Layover Time: 0hr 57min; Total Trip Time: 6hr 30min OPTION 4: 6hr 40min via Dallas Fort Worth (DFW)

YYC - DFW American Airlines Flt 0694 Dep 02:10pm 16Oct,Fri

DFW - MEM American Airlines Flt 1218 Dep 08:25pm 16Oct,Fri

Flight Duration: 5hr 00min; Layover Time: 1hr 40min; Total Trip Time: 6hr 40min