Really enjoyed the read, but I don't understand the line about going from 500km/h - 1000km/h in 5 seconds... treetop level or otherwise. Is that really possible

Really enjoyed the read, but I don't understand the line about going from 500km/h - 1000km/h in 5 seconds... treetop level or otherwise. Is that really possible? I think my math is off if so. Mass with a 900kg fuel load looks to be around 12,000kg Max thrust is 162kN for both with afterburner. 500km/h = 139m/s 1000km/h = 278m/s Going from one to the other in 5s means an average acceleration of 27.8m/s^2... or almost 3 g, which is monstrous! But how does this work? Solving F=ma for a gives a=F/m = 162000/12000 = 13.5m/s^2 And that's before accounting for the not insignificant thrust required just to overcome the aerodynamic drag. Is it just an understandable overestimation of the acceleration due to the direct experience of it? Or am I missing something? Either way, awesome.