first draw a sketch of the described situation.
With your values the plane flies at an altitude of 346,410 feet that's nearly ten times the normal altitude of a long ditance flight. (Presumely the observed angle is 3°(?))
The given rate of change leads to a speed of (roughly) 8,155 miles per hour which is ten times the speed too a normal aeroplane is flying.
The fact that nobody has answered yet indicates that your problem contains some severe mistakes.
PS.: I tried to attach a diagram but I cann't upload the file. So sorry.