Delayed: what makes a flight run behind schedule?

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Delayed: what makes a flight run behind schedule?

Flight delays can be frustrating and inconvenient for waiting passengers.

A flight can be delayed by a few minutes, a few hours or even by a couple of days. Not surprisingly, a delayed flight will probably inconvenience your plans at the other end - especially when you face a long wait or when the rescheduled time is unknown.

The stats

Of the 35 major international airports recorded by the Flights Stats report, four had less than half of their flights leave on timei. At the bottom of the ranking was Quangzhao Airport: only 22% of their flights left on time or within the grace period of 15 minutes after the scheduled flight time. Performances at other major Chinese airports in Beijing and Shanghai also fared dismally, with only 30% and 34% of departures leaving on time. The only other airport with an on-time performance below 50% was Istanbul, Turkey. The rest of the 35 airport performances fell between 50% and Tokyo's impressive 92%.

For passengers relying on a domestic flight to meet their next flight connection to go overseas, a delay or cancellation can mean that you miss the next leg of your journey. The Department of Infrastructure and Transport (BITRE), which records and reports "Airline On Time Performance" found that only 79.3% of domestic (Australia) flight departures left on time in March 2013ii. Unlucky for some, the month saw 1.5% of domestic flights cancelledii!

What delays a flight?

Flights can be delayed by any number of situations, including bad weather, industrial action, and knock-on effects of delayed flights or problems at another airport. With connecting flights, a delay can prevent you from making your next flight in time.

The domino effect of problems at a particularly busy ‘hub’ airport can disrupt airline and airport schedules across the world. A handful of flights departing Australian airports rely on flights arriving from somewhere else first, a delay in Dubai or Europe could potentially disrupt flight schedules. Prolonging take-off time further, a delay may require reshuffling the airport's take-off timetable and your flight may have to wait a while for an opening in the schedule until it can leave!

Another reason for delayed arrival at an airport might be if there is a queue of planes waiting to land before yours or if you need to wait out bad weather on the way in. On top of this, Sydney Airport has a curfew that prevents flights from landing and taking off between 11pm and 6am (flights that do incur a fine)iii. So, if you're due to arrive in Sydney and your flight is delayed long enough to push your landing time into that curfew period, you may have to wait even longer to board your flight so that the rescheduled landing time will be after 6am.

Preparation problems

If ground staff or the flight crew are concerned about the mechanics of the plane, or if they identify a safety problem, you may be delayed while they fix the issue. What if a bag has been checked in and the passenger doesn't turn up for the flight? That's another cause of delay, as the airline is required to remove the checked luggage before take-off.

Weather and air quality

Fog, strong winds, heavy rain, hail, snow and other bad weather can cause a flight to run behind schedule. Some flights can't take off until they are sure that the bad weather has cleared up at the destination. Bigger events like floods or cyclones can also cause prolonged delays (up to several days) or even force airlines to cancel flights altogether.

Admittedly not weather-related, there are some events that affect air quality and visibility that also disrupt flight timetables. These include events like ash clouds from volcanic activity or fire-related haze. A volcanic eruption in Iceland in 2010 caused air traffic chaos for at least a week with 95,000 flights cancelled throughout Europeiv. Similarly in 2011, ash from a volcanic eruption in Chile disrupted flights across South America, New Zealand and Australiav.

From where you'd rather be... many situations cause delays, including bad weather and industrial action.

Industrial action

Airports and flights depend on a number of different unionised groups including ground staff, maintenance crew, engineers, check-in staff, and flight crew in order to operatevi. Dissatisfaction within one of these groups may result in industrial action that can ground flights or cause heavy delays.

There's very little you can do about a delayed flight. If you worry that your flight may be delayed by foreseeable circumstances - like bad weather or industrial action - it's best to check your flight's status before heading to the airport. Your airline and the airport should be able to keep you up to date on your flight's status via their website. If you've heard nothing, then head off to the airport so that you can stay in touch and ensure that you don't miss your flight!

i Flight Stats, 2013, Airline and Airport On-time Performance Report: Summary of airline arrivals and airport departures for the period March 1 2013 through March 31 2013, p.10,

ii BITRE, 2013, Airline On Time Performance Statistics: March 2013,

iii Department of Infrastructure, Transport, Regional Development and Local Government, Airport curfews: general information,

iv BBC News, 2010, 'Volcano ash flight ban 'cost London 100m'',

v Schneider, K., et al., 2011, 'Live updates: Flights disrupted by Chilean volcano ash',

vi AAP, 2011, 'Qantas disruptions could last for weeks, union warns',