The following problem is posed on the final exam for M121:
Using the air_alliances and air_routes collections, find which alliance has the most unique carriers(airlines) operating between the airports JFK and LHR , in either directions.
Names are distinct, i.e. Delta != Delta Air Lines
src_airport and dst_airport contain the originating and terminating airport information.
Does this question intend to use direct routes only (where the number of stops is zero) or are routes with one or more stops also to be considered?