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35 Aircraft not already connected to a generator or ground resulting in required rescheduling or rebooking of flights, power unit keep their engines running (at least minimally) under-capacity flights, possible special movements of aircraft, to maintain cabin and instrument power, and and flight personnel shifted to cover for delayed airline Available gates fill up and additional arrivals park elsewhere. employees. Furthermore, depending on contract terms, air- line crews who experience extended wait periods as a result of Many of the costs could be classified as "wasted time." lightning (or other weather) delays may become restricted in While we considered it appropriate to consider such wasted their ability to maintain their flight schedules. Reserve crews time as a cost, it is important to distinguish between "lost may be available at base airports, which would minimize the opportunity" time (time that could have been spent doing impact on flight operations. At other airports, flights may something else), delay or annoyance time (passengers not need to be canceled to allow the crews the requisite daily rest being able to get to their next destination, or crew not being period. This could result in impacts on flight schedules and able to move to their next flight assignment), and direct costs, produce a real cost to the airline. Table 1 presents a summary such as fuel costs for idling engines, which entail real dollars of potential costs incurred by events of varying duration. that have to be paid by the person or entity incurring the cost. With the exception of the possible total closure of an air- While it is reasonable to include some effective hourly "cost" port because of the lack of ramp capacity to accept landing associated with passenger delay time, nobody really pays the aircraft, lightning-based ramp closures should not result in delayed passengers cash (or even provides flight coupons). FAA-imposed en route delays or ground holds. There may be Flight crews may well waste some time during a ramp closure, some exceptions, but most downstream impacts from ramp but to the extent they are salaried or paid by flight time (and not closures will be due to delayed aircraft departures by the total time), ramp delays do not necessarily involve a true cost affected airline, resulting in some missed connections to desti- to the airline unless flight personnel reach their daily or weekly nation airports (because many passengers will not be connect- service limits. Baggage handlers may well be idle during a ramp ing at the destination airport, they won't miss any connections, closure, but unless they get so far behind that they have to work even though they arrive late). These delays would be similar overtime, they may be able to get caught up during their to simple mechanical delays that can affect individual flights. normal scheduled work hours at no extra cost to the airline. Perhaps the largest of such impacts might be from aircraft not Unexpected or unscheduled overtime, on the other hand, reaching their final scheduled destination of the day, which could represent a very significant "real" cost. would mean that the airline's aircraft will not be positioned It would seem that flight delays would always entail some for the next day's flights. very significant real costs, but the analysis of the costs is not straightforward. Passengers and crew making intraline con- Approach to Cost Savings Analysis nections at the affected airport should still be able to make their next flights, since all loading and unloading at the air- There are many possible ways to address this sort of analy- port for that airline is suspended across the board. Flights sis. Initially, we examined the use of a "queue" delay reduction (or passengers, or crew) making interline connections to their approach or a "linear" delay reduction approach, as de- destination airports, on the other hand, could miss connections, scribed in Delay Causality and Reduction at the New York City Table 1. Cost effects for delays of various duration. Short Duration Medium Duration Long Duration Cost Item Delay Delay Delay Passenger Time Yes Yes Yes Direct Cost to Airline Minimal Some Likely Ripple Effect Some Some Likely En Route Delay None Unlikely Possible Notes: Short duration is defined as less than or equal to 60 min. Medium duration is defined as greater than 60 min and less than or equal to 135 min. Long duration is defined as greater than 135 min.