Hub & Spoke:
Advantages - a strong hub system provides connnections between hundreds of city pairs, and can offer seemless transportation from small cities to large cities that would otherwise not be available. Example, getting from Mobile to Milan could be very difficult if DL
did not have a huge hub in ATL
Disadvantages - Many cities that would otherwise be connected with nonstop service must now travel via the hub, adding travel time. Hubs are big and expensive to operate, and do not optimize aircraft usage (lots of planes sitting around waiting for a flight complex to depart), weather or delays can upset the entire airline system.
Point to Point:
Advantages - Quick, easy and effecient connections between major cities. Reduces travel time and eliminates connections. Nuch easier to schedule and optimizes aircraft usage.
Disadvantages - Many city pairs cannot support nonstop service, smaller cities lose vital airline connections, reduction in frequency on flights to major destinations.
Hubs are here to stay, its the only way for a large airline to provide service through out its network and maintain connections to cities large and small world-wide. That being said, we will see some fragmentation in the airline system, with flights being offered to more destinations from various hubs plus there will be flights that by-pass hubs altogether.
The airline industry is slowly changing to traditional carriers, offering world wide service via hubs and to the new LCC carriers, based on a point to point system but only offering service in markets where there is a profit to be made. Short-haul flying (which is point to point) is more and more dominated by lower fare airlines.