Everytime, i fly any of the boeing planes around 35,000-39,000 ft. i get a message that says 'overspeed' when i'm flying at 300 knots, is there any way i can fly faster then that? because this one time, i was flying the F-15 jet following a boeing airplane and they were going faster then 300 knots at the same alt. i was flying in

Full throttle, nose down.

Seriously though Andrew has covered it.  Your airspeed indicators display airspeed calculated via a pitot tube which measures the pressure of the air flowing over your aircraft.  The faster you go the higher the pressure in the pitot tube and thus the greater the indicated airspeed.  As your altitude increases the barometric pressure drops and your indicated speed is less than your actual speed.  So at 2000 feet your airspeed will be eg 200kts but at 30,000 feet you will have an indicated speed of eg 150kts but be travelling just as fast.

Great name by the way.  I don't know where your tail is though.

Will

In a heavy at that height and speed you should be flying by mach not airspeed.

If you check your mach figure I'm sure you'll find it at something like 0.8 - 0.85 which is right for this aircraft.

If that's not fast enough suggest you try to get hold of one of the Concordes although I think that they have now all been allocated to various museums and such

Hi man,

         Just to tell you that when you are flying with an airplane powered by turbines, at around 40000 feet and more, your relative speed (air speed) is twice than your ground speed. So if it is wirtten 300 kts on the airspeed gauge, in reality, you are going at 600 kts at the groud level. You can validate that in some book of mechanic of flight.

                        Cheers