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Air Traffic

Air traffic delays are typically consequences of other problems such as weather or congestion both on the ground and in the air. Programs such as ground stops or the invoking of slot times if not already in place, alleviate some of this congestion by providing an orderly flow of traffic (albeit with delays) in and out of airports. There may be other problems such as systems failures, navigational aid failures or out of service conditions, power failures, or communications issues but mostly these are uncommon. In some airports, the loss of a high-speed taxiway (enabling aircraft to exit a runway expeditiously) due to works, for example, may result in longer runway dwell times as aircraft slow to turn off the runway at a suitable exit point, with a consequential reduction in the rate of approaches being conducted. In the event of an aircraft becoming disabled on a runway (e.g., due to a burst tyre or loss of steering) this is likely to close the runway until removal can be effected. In a singlerunway port, a lengthy removal process may well result in diversions as inbound aircraft will not normally be carrying additional fuel to hold for very long (other than mandatory reserves). Increasingly of concern are airspace closures due to industrial, staffing, military needs, or due to political tension and areas of conflict.

IOC response

The IOC response will depend on the causal factors and the extent of АТС delays. Usually, problems caused by weather and congestion will become evident quickly as delays begin to emerge and revised slot times advised. IOC responses may initially follow a somewhat predictable pattern of sourcing information:

  • a) What aircraft are being delayed inbound and for how long?
  • b) How much fuel is each aircraft carrying?
  • c) What alternates have they each nominated?
  • d) How are the alternates coordinated so as to prevent traffic congestion and/or overwhelming the resources at any particular alternate(s)?
  • e) How long can each hold before diverting?
  • f) What aircraft are being held on the ground?
  • g) Have these aircraft sufficient fuel on board or do they need additional fuel to enable holding given the circumstances?

The IOC actions regarding the above information are likely to be similar to the responses in weather situations, and therefore are not repeated here. However, in the case of a runway closure, the IOC will need specific information:

  • a) What are the circumstances of the disabled aircraft?
  • b) How long is the runway expected to stay closed?
  • c) What aircraft are holding at present?
  • d) What other aircraft are due to arrive?
  • e) How much fuel and holding do these aircraft have?
  • f) What aircraft are due to depart?
  • g) Will they be disrupted, and if so, to what extent?

Subject to these answers, the time of day and other circumstances, further considerations such as proximity to curfews, crew hours limitations, connecting flights, and so forth may also be of relevance. Based on the information gleaned through this process, the IOC can then establish a course of action.

  • a) Should the disabled aircraft occupy the only runway available and the expectation is that removal will take considerable time, the IOC would normally wish for inbound aircraft to hold as long as practicable as long as there is a strong likelihood of landing.
  • b) However, unless these flights are carrying sufficient fuel to hold for extended periods (unlikely if they are only carrying standard fuel reserves) they will most probably divert promptly, unless the problem is very short term. The IOC then will probably elect to have the aircraft refuelled and sent back as soon as it is evident that a landing can be accomplished.


Disruption due to crew-related issues can be caused by reaching duty hours limitations, crew sickness or fatigue, crew rest requirements or exceptional circumstances such as this example below:

At a destination airport, a technical crew operated a smaller version of a particular type of aircraft one evening, and then took crew rest, as planned. (The crew from the previous day operated the aircraft out.) When the crew signed on the next day to take the flight back to the hub, they found that the airline had upgraded the aircraft to a larger model of the same type. While licensed to fly the larger version, they were not endorsed to taxi and turn the larger aircraft at one end of the runway at this particular airport, rendering the crew unable to operate the flight, and requiring the airline to position another crew to that port, resulting in a lengthy delay.

Crew sickness at a crewing base is not normally disruptive due to (a) reserves who may be on duty at the airport and available to fly immediately, or (b) other reserve crews who are not at the airport but are ‘on call’. However, crew sickness at an ‘out station’ where back-up crews are not resident, is more troublesome and calls for alternative action. The IOC will seek to establish the following:

  • a) Is there a replacement crew at this port? (sometimes there may be a crew taking crew rest for a number of days, who could be called to operate an earlier than planned flight). Considerations are whether they have had the legal rest period, and whether they have consumed any alcohol within the legally permitted time prior to a duty period. Sometimes, a more expeditious solution may be to wait for the original crew members to recover and present fit for flying (of course, this is dependent upon the nature of the problem).
  • b) If there is no crew at this port, is there one at a nearby port who could be positioned (dead-head) to operate? Achieving the intended flight schedule may be possible providing the total duty time (including positioning) is within limits. If the replacement crew have to take additional rest, little may be gained. Perhaps, though, achieving some of the schedule is possible by operating into a midway port en route, and thus reducing the duty time. Of course, there needs to be a replacement crew sent out to this port to continue the flight.

IOC response

IOC strategies can be quite novel at certain times to recover from a crew-related disruption. In the case of pilots’ ToD limits for long-haul operations there are a number of options that may be invoked.

  • a) If a ToD with two pilots is the limiting factor, can the ToD be increased by adding an additional Pilot for the flight, or can the ToD be reduced by operating via an interim port and replacing the original crew members?
  • b) If the Captain (or Aircraft Commander in some airlines) becomes ill, the flight cannot operate without another Captain, but if a First Officer has reported ill, consideration is given as to whether another Captain can replace the First Officer (i.e., have two Captains operating, although only one is the nominated Pilot in Command). If this is possible, the ‘fill-in’ Captain must be right-hand seat endorsed. Of course, any plan that robs resources earlier than planned, needs to cover these subsequently, so there is a knock-on effect.

In the case of long-haul operations with heavy or augmented crew complements (i.e., three or four flight crew members), other options come into play:

  • c) If the flight plan can be shortened (i.e., more direct routing), the ToD time may be reduced to an extent that a three-crew complement can be used instead of the rostered four-crew complement.
  • d) One way to shorten a flight is to cruise at a slightly higher speed, which may satisfy the ToD limit, but may require an increase in fuel uplift and will certainly raise the cost factor of the flight.

Cabin crew

There is a legal requirement for a minimum number of cabin crew due to the need to provide safety on board and, in particular, to operate exit doors and evacuate passengers in an emergency. Often, airlines may carry additional crew members over and above this legal requirement. This comes at a cost of course, but the rationale is to provide additional levels of service, especially for premium class travellers. In the case of a shortage of cabin crew (e.g., due to sickness), there are a number of strategies that can be employed to overcome the shortage.

  • a) Dispensation to operate with reduced crew (this will probably need agreement from both the union (if applicable) and Customer Service Manager/Director - the Senior Flight Attendant on board) but must still meet regulatory requirements. (All doors must be staffed for evacuation considerations, but service levels may be slightly diminished.)
  • b) Restricting the passenger load (the ratio of Flight Attendants to customers varies from airline to airline, but the regulatory requirements must still be met).
  • c) If an augmented technical crew (i.e. three or four pilots) is operating the flight, the most junior Pilot (e.g., Second Officer) could be stationed at one of the doors just for take-off and landing.
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