Getting the time right

Scheduling correctly is a difficult art: if too long a time is blocked for a flight, the airline will not be able to make best use of resources - staff, airframes, infrastructure. But too short a time can arguably be worse as late flights generate rotational delay with late incoming aircraft and passengers from previous flights having to be accommodated. When flights leave on time but arrive after the scheduled time of arrival, they cause reactionary delays.

So a lot depends on getting it right!

Luckily, help is at hand. CODA, the Central Office for Delay Analysis at EUROCONTROL, has developed new indicators that complement the existing punctuality indicators and are very helpful indeed in assessing the airline’s punctuality - as Norwegian Air Shuttle has recently discovered, much to its satisfaction (see story below).

There are two of these indicators:

  • The Block Time Overshoot (BTO): this gives the percentage of actual block times which are longer than the scheduled block time. The BTO of flights operated in Europe is typically between 25% and 35%.
  • Delay Difference Indicator-Flight (DDI-F): this is the difference between the arrival punctuality and departure punctuality expressed in minutes. Flights operated ahead of schedule can therefore have a negative delay figure. The DDI-F of flights operated in Europe, with a tendency to be slightly negative, is typically around -3 minutes.

For more information on these indicators, read the seventh issue of “Trends in Air Traffic”, Planning for delay: influence of flight scheduling on airline punctuality.

The Norwegian experience at Gatwick

On time performance (OTP) is extremely important for Gatwick and they have a dedicated airfield improvement team to help airlines make faster turnarounds. In March last year, the team spoke to all their top airlines to find out how they could help improve OTP through block times, crew processes and scheduling.

Having persuaded Norwegian Air Shuttle to help them see how their operations could be streamlined, Gatwick set up a workshop in December 2011 with them and people from various divisions in the Network Management Directorate - airports, operations and monitoring/reporting. The objective: to help make Norwegian’s summer 2012 performance better than the year before.

Using the CODA scheduling indicators for the entire Norwegian network - and not just for the Gatwick connections - they found that the root cause of inbound delays at Gatwick could be traced to delays at two or three sectors before Norwegian aircraft arrived at Gatwick.

Having this kind of information helped the airline improve their performance at other legs and Gatwick took a series of measure to improve Norwegian’s turnarounds at their airport. A preliminary analysis of arrival delays at Gatwick in spring this year already shows a 45% reduction in the average delay per flight.

Next steps

Gatwick is now extending the use of the BTO and DDI-F indicators to other airlines at Gatwick, so as to improve winter schedules.

BTO and DDI-F can help you, too: they are embedded in the tailored CODA operational report for airlines.

To find out more, contact the CODA team