Cut down on congestion? Now a traveler can make TWO trips to the airport (one to check in, one to actually leave) so just how will that relieve congestion.... and as for all that luggage: stored where? Transported to some holding area... giving up space that could be used for any number of useful functions: parking, shopping, customs shake downs..... also give larceny minded baggage handlers more time to leisurely go through your belongings pre-flight.