Airport Challenge

This is a simple app that allows planes to land and takeoff from an airport.

Classes

Plane - This class instantiates a plane object with an instance variable @flying which is initial set as flying assuming planes are in the air until landing at an airport.
Airport - The airport class contains methods that deal with the landing and taking off of plane objects.

An airport initializes with an empty plane array to store planes and a default capacity (20).
THe land and takeoff methods set the plane variable flying to false and true respectively so that the attr_accessor flying can be called on a plane object to determine whether is is currently in an airport or in the air.
Both land and takeoff methods contain guards against the edge cases of landing and taking off in stormy weather and also only landing / taking off if the plane is already flying/landed.
The land method also guards against planes landed while the airport is at maximum capacity. This is determined by the method full.
The stormy? method outputs true with 10% probability and is used for testing weather conditions within the land and takeoff methods.