Answer
6.3 kilometers
Work Step by Step
We first need to find the difference in pressure between the inside and the outside of the cabin:
$ p = 62 \times 10^6 kPa - 1.01 \times 10^5 Pa = 6.19 \times 10^7 Pa$
We now can find how far it can go down:
$ h = \frac{P - P_{atm}}{\rho g}= \frac{ 6.19 \times 10^7 - 1.01 \times 10^5}{1000 \times 9.81} = 6300 m = 6.3 km$
