ANSWERS: 3
  • The Boeing 747 cruises at around 0.85 Mach, but in answer to how fast "can" one go, the answer is that Vmo/Mmo (maximum operating speed/mach) for the earlier versions is 0.89 Mach and for the 747-400 it's 0.92 Mach. (0.92 mach is over 600 m.p.h)
  • It's more confusing then it seems. They fly mach numbers and mach numbers equal different ground speed depending on the temperature. The top operating speed (never exceed speed) for a 757 would be .86 which equates to about 550 MPH groundspeed at somewhere around -20 degrees Fahrenheit (my guess for the temperature between 30,000 and 40,000 feet) - if the pilots kept the speed up in the descent and maintained a mach number of .86 this would rise to around 630 mph groundspeed as they neared the ground on a warm day. They could probably go a little faster than this as limiting speeds on airliners are usually created with some safety margin - assuming they could push mach .95 in a dive without suffering some sort of control hang-up due to the shock wave a plane develops nearing the speed of sound this would equal about 670 mph groundspeed near the ground - I chose .95 mach because somewhere around this point the speed of the air flowing over the wings would start to go supersonic (air over the top of the curved wing flows faster - thus creating lift). This would create severe aerodynamic problems which would probably cause a discontinuation of the beverage service (probably because the wings would come off) - hope this helps - bottom line is at altitude top speed is probably about 600 mph groundspeed and near the ground around 650 mph - of course all this doesn't take into account winds - add a 100 mph tailwind and you've got groundspeeds over 700 mph - pretty amazing for a thin aluminum tube!! The Boeing 747-400 can exceed 600 mph if you aren't careful.
  • i have travelled many times on 747 to bangkok and the video footage i have shows a ground speed of 651 mph is this different to the speed it is going

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