Answer:
381623 ft
Step-by-step explanation:
Since the airport altitude is 20000 ft and the pilot needs a 2° descent, to calculate the distance of the airplane at the start of this approach, first this is represented in the diagram attached. The distance from the runway at the start is x.
[tex]tan(3) = \frac{20000}{x} \\x=\frac{20000}{tan(3)} \\x=381623ft[/tex]
The airplane is at a distance of 381623 ft away from the airplane runaway at the start of the descent.