Why is the aircraft at "fullspeed" hundreds of feet off the ground?.
I think some posters do not realise how much power these types have at low level. Even if the pilots reduced to 75% N1 (737 Unreliable Airspeed thrust setting? Mine's 80% N1) once the gear is up, that thing is going to accelerate like a rocket. After 5 minutes at low level and in basically level flight, 380 is very likely, especially if the system is "helpfully" trimming forward as you progress!