I've seen some RC airplanes and helicopters do a lot things that would be impossible in the "real world".
The answer is simple: Lots of thrust and very little weight. Up until the latest generation of fighters: F-15, 16, 18 ,etc, they didn't have the 1-to-1+ thrust to weight ratio. Now, as long as you have airflow over the controls, you can point to any way you want as long as you want.
The T-38 was, and still is, a hot fighter-trainer. But it weighed 10,000 pounds with half a tank of fuel and put out 4,000 pounds of thrust in full burner. It would go straight up only until the initial airspeed was depleted.
Lots of CL & RC models will take off vertically and accelerate.