are the Greek islands with July/August having more than ten times the winter traffic, as Jet2 is the most seasonal among low-cost carriers with July having seven times the January traffic, whereas legacy carriers are much less with only 85/115% variability. Assets and financing Airline financing is quite complex, since airlines are highly leveraged operations. Not only must they purchase (or lease) new airliner bodies and engines regularly, they must make major long-term fleet decisions with the goal of meeting the demands of their markets while producing a fleet that is relatively economical to operate and maintain; comparably Southwest Airlines and their reliance on a single airplane type (the Boeing 737 and derivatives), with the now defunct Eastern Air Lines which operated 17 different aircraft types, each with varying pilot, engine, maintenance, and support needs. A second financial issue is that of hedging oil and fuel purchases, which are usually second only to labor in its relative cost to the company. However, with the current high fuel prices it has become the largest cost to an airline. Legacy airlines, compared with new entrants, have been hit harder by rising fuel prices partly due to the running of older, less fuel efficient aircraft. While hedging instruments can be expensive, they can easily pay for themselves many times over in periods of increasing fuel costs, such as in the 2000–2005 period. In view of the congestion apparent at many international airports, the ownership of slots at certain airports (the right to take-off or land an aircraft at a particular time of day or night) has become a significant tradable asset for many airlines. Clearly take-off slots at popular times of the day can be critical in attracting the more profitable business traveler to a given airline's flight and in establishing a competitive advantage against a competing airline. If a particular city has two or more airports, market forces will tend to attract the less profitable routes, or those on which competition is weakest, to the less congested airport, where slots are likely to be more available and therefore cheaper. For example, Reagan National Airport attracts profitable routes due partly to its congestion, leaving less-profitable routes to Baltimore-Washington International Airport and Dulles International Airport. Other factors, such as surface transport facilities and onward connections, will also affect the relative appeal of different airports and some long-distance flights may need to operate from the