anchor.diff:      alliances: function(){
         return _.uniq(this.get_flights_values("alliance", true));
       },
  -
  +    airports: function(){
  +      var airports = [];
  +      _.each(this.flights, function(flight){
  +        airports = airports.concat(flight.airports());
  +      });
  +      return airports;
  +    },
       airline_duration: function(){
         return _(this.list()).chain().
         reduce(function(hash, flight){
  
positive.code:     alliance: function(){
        return this.data.alliance;
      },
      origin: function(){
        return this.data.origin;
      },
  
negative.code:     memoize: [],
      context: function(){
        var data = {};
        var self = this;
        _.each(["airlines", "airports"], function(name){
          var list = self.direct_flights[name]();
          if(self.return_flights){
            list = list.concat(self.return_flights[name]());
          }
          var collected_data = {};
          _.each(list, function(id){
            collected_data[id] = NANO.api[name].get(id);
          });
          data[name] = collected_data;
        });
        return data;
      },
  