text: function Airport(capacity) {
    this.hangar = [];
    this.capacity = capacity || 5;
  };
  
  Airport.prototype.isFull = function() {
    return (this.hangar.length >= this.capacity);
  };
  
  Airport.prototype.land = function(plane) {
    console.log(this.isFull())
    if (this.isFull()) { throw new Error('Airport is full'); }
    plane.land();
    this.hangar.push(plane);
  };
  