Delay is message that something has gone wrong with the planned operation. When this message is suppressed by incomplete and unreliable reporting, the problems may reappear, grow, and spread widely, generating severe losses. Traditional reporting practices hide a great deal of delay problems inside and outside of the airline environment. Among them are unreported delays within the ‘grace’ period and schedule buffers. Let’s see how much they distort the true picture about delays: In industry reports, flights are counted as delayed when they are 15 or more minutes late compared to the reference schedule.
When unreported delays within the ‘grace’ period between zero and 15 minutes are included, the statistics show that hardly half of the scheduled flights departed on-time. There are a number of problems associated with ‘grace’ period. Firstly, it ignores the distinction between operational and commercial values of short and long-haul flights. The value of, say, a one-hour short-haul flight that is delayed for 15 minutes, which equals 25% of the actual block time (typical for majority of European domestic routes), cannot be compared with a long-haul flight.
Furthermore, it does not allow for true reporting on causes of delays – a flight delayed for 14 minutes will not be registered as late even if it caused a longer delay due to the missed ATC slot. In addition, it sets an example that inefficiencies are acceptable. How can other performance targets within the airline be set close to 100% when the whole industry holds that a 15 minute delay is tolerable, or, when wiping off 20-30% of flights delayed between 0 to 15 minutes has become an industry norm.
Airlines are building the most predictable delays into their schedules as a response to the growing number of flight delays at congested airports, especially critical for passengers with tight connecting times. These schedule buffers obscure the true picture about system inefficiencies, and make the historical trends look smoother than they really are, as in the following example: If a flight routinely experiences a 20-minute wait in a departure queue and those 20 minutes are added into its flight schedule, it will continue to be delayed for 20 minutes, but will show as ‘on time’ in a punctuality report and may never be further scrutinised as delayed. By adding up this buffer time to 15 minutes of ‘grace’ delay, we come up to 35 minutes of unreported delays.
Measuring delays with respect to published schedules significantly underestimates the true burden of growing congestion. After accounting for schedule padding for routine congestion on domestic routes in the US, it has been found that delay is actually between 57 and 96 percent higher than what airlines report. While buffers are meant to serve as a protective shield against passenger delays, the highly padded schedules generate costs that often highly outperform the benefits. Airlines end up charging passengers more for more disrupted journeys and the extended trip times.
The volume of costs hidden behind schedule buffers could be staggering, like in the following examples:
- The time a major European airline spent in airborne holding at home base amounted to the equivalent of having approximately three aircraft unavailable for the whole season, or about 300 passengers holding for 8 hours every day.
- The schedule buffers used by major operators on short haul routes between congested airports like London Heathrow and Paris Charles de Gaulle take five hours of aircraft utilisation each day, which could be more effectively used elsewhere.
Schedule buffers disguise the system inefficiencies and are difficult to master. They push airlines into a dangerous zone of low productivity and higher costs, without much guarantee that their operation will be as punctual and competitive as expected. Just look at published on-time performance for airlines with heavily padded schedules operating to Heathrow. They are far from enviable. Too much buffering is a clear sign that there is a time for change in airline strategy.
