The Evolving Airline Industry: Impacts on Airports
2.4 Airline Operations at the Airport
op-timized to reduce costs, increase revenues, and maximize profit under what are typically assumed to be favorable operating conditions. Unfortunately, almost every day presents a variety of unexpected and unplanned events that force any airline to deviate from its op-timized schedule.
Dealing with “irregular operations” requires airlines to revise their planned schedule right up until the flight departs or is cancelled. A cancelled flight can seriously disrupt aircraft rotations, crew schedules, and maintenance plans, not to mention passenger trips.
Under conditions of disruptions and/or flight cancellations, the primary objective for the airline is to return to normal operations as quickly as possible. In this effort to get the airline
“back on plan” with respect to the planned timetable, flight cancellations or aircraft rerout-ing sometimes take precedence over passenger convenience. The next section describes the characteristics of airline operations occurring at the airport that can contribute to these de-viations from the planned schedule.
• The availability of equipment and ground crew resources, operated by both the air-line and the airport.
• Air traffic control (ATC) congestion and delays, both at the airport and those that affect flights en route to or from the airport.
If the airport is a connecting hub for the airline, station control also tries to ensure that passengers and baggage make their connecting flights. They must trade off the costs and benefits of holding a flight at the gate beyond its scheduled departure time when one or more incoming flights have been disrupted and arrive later than planned. Delaying the de-parting flight to accommodate passenger and baggage connections improves the passen-gers’ travel experience and reduces the costs to the airline associated with passenger re-booking, including meals and hotel accommodations, and delayed baggage delivery to the destination. On the other hand, holding the flight adds to airline operating costs and can result in further down-line delays for the next scheduled departures of the same aircraft and/or crews.
The “turnaround” activities associated with each arriving and departing aircraft at an air-port are central to keeping the airline operations running smoothly and are major factors in delays that can affect airport operations as well. These activities include deplaning passen-gers and baggage, cleaning and catering the aircraft, performing required security checks, refueling the aircraft, and then boarding the passengers for the next departure. Completion of the flight turnaround process within the scheduled turn times is a critical factor in the airline’s ability to operate its planned schedule with minimal delays. Although a signific-ant portion of airline delays are associated with schedule disruptions away from the gate (e.g., taxiway queues awaiting takeoff or airborne delays resulting from en route conges-tion), many other flight delays are encountered and absorbed at the gate, which affects the overall operation of the airport.
Most airlines incorporate “buffer” time into the planned schedule for each flight to take into account what can be substantial variability in actual flight block times due to vari-ous delays. Figure 2.8 shows the distribution of actual block times for a large sample of flights that operated on the New York/Newark (EWR) to Los Angeles/International (LAX) nonstop route. The median block time is 363 minutes (or 6:03) for this 2450-mile flight, while the dispersion is quite large. Actual block times ranged from about 310 to almost 500 minutes. (Note that EWR can be a very congested airport subject to substantial air traffic delays, which explain the long delays apparent in this distribution.) If an airline published a block time of 363 minutes, 50 percent of its actual flights would arrive after their scheduled arrival time (but, of course, 50 percent would also arrive early!). Increasing the planned block time reduces the probability of late arrivals but at the same time increases the like-lihood of early arrivals at the destination airport. Early arrivals not only lead to reduced
utilization of aircraft and crews, they introduce their own form of “irregular operation” for the airline, as gates, ground crews, and baggage handlers might not be available at the time of the early arrival.
FIGURE2.8 Distribution of actual block times. (Source: Skaltsas, 2011.)
Decisions made by airline schedulers regarding planned departure, arrival, and block times can significantly impact the operations of the airline at an airport, and thus the oper-ations of the airport itself. For any given flight schedule, the operational variability for an actual flight on a given date can result in flight delays, missed passenger and baggage con-nections, irregular operations, and even flight cancellations for the airline. For the airport, this variability can create problems in terms of gate availability for other scheduled flights.
Figure 2.9 shows the distribution of gate delay times for the same sample of EWR-LAX flights. Although some flights departed the gate as much as 10 minutes before scheduled departure time, the median gate delay time was 5 minutes and the average was more than 17 minutes. These gate delays and their variability, in particular, make it more difficult for both the airline and the airport operator to optimize the utilization of gates, ground crews, and related scarce resources.
FIGURE2.9 Distribution of gate delay times. (Source: Skaltsas, 2011.)
Whether the delay occurs at the departure gate or during any of the subsequent stages of the flight’s operation, a late arrival at the destination airport is an inconvenience for pas-sengers. For a flight into an airline’s hub airport, an arrival delay of even 30 to 60 minutes can translate into a major disruption of travel plans if it means that passengers cannot make their connecting flights. At best, a missed connection delays the passenger’s arrival at their destination by several hours, depending on when the next flight from the hub to the pas-senger’s destination is scheduled. However, with increasing airline load factors, reaccom-modation of disrupted passengers on later flights becomes more difficult due to a lack of available seats.
Delayed flights complicate operations for both the airline and the airport operator. Dis-rupted passengers end up spending substantially more time (and perhaps more of their money) at the airport. They inevitably end up with a negative perception of their overall travel experience that they typically attribute to both the airport and the airline (or in some cases, incorrectly to the airport alone). For airports wishing to develop and improve cus-tomer perceptions of their services, it is therefore important to identify ways in which air-port operators can collaborate with airline ground operations to reduce the negative impacts of flight delays, not only on operational factors but also on the passengers themselves.