Disruptions due to maintenance (or technical) problems are an everyday occurrence in an airline operation. There are numerous reasons of course - from a broken tray table to an engine change, but whatever the problem, each has the potential to disrupt a flight. Most commonly, disruptions occur during service; that is while the aircraft is engaged in scheduled activities. Unserviceabilities may be discovered while undertaking ground inspections during turnarounds between flights, or componentry may fail during any stage of the flight. Aircraft may be grounded and require Engineers and parts before being permitted to continue, or may be cleared to fly with some performance limitation or other restriction. Aircraft can also arrive on the line (at the gate) late after overnight work, can be damaged during handling or ground servicing, by passengers (on-board breakages), or by weather (e.g., hail damage or lightning strikes) and so forth.

IOC response

Maintenance disruptions can be another area of significant challenge in the IOC. Timely and appropriate engineering advice is crucial to identifying and assessing a problem, and then determining the most efficient course of action to return the aircraft to service. The difficulty for IOCs lies in taking the expert advice on the one hand, while on the other, determining how best to deliver schedule recovery to customers. Depending on all the circumstances of the maintenance issue (and other variances), the IOC will require some or all of the following information:

  • a) What exactly is wrong with the aircraft? (Initially this may be hard to determine without due expert input.)
  • b) Where has the initial advice come from? (This is a most important clarification, as early advice may often be communicated by a well- meaning but innocent third party, with little or no engineering knowledge.)
  • c) Are licensed Engineers (appropriate for the problem) available to


  • d) Can they fix the aircraft?
  • e) Do they need to fix the aircraft (i.e., can it operate on an MEL? This may be possible with a speed or height limitation for example - advice from Engineering will lead this discussion.)
  • f) What is the ETS (estimated time of serviceability)? (This provides the first guide (though perhaps crude at an early stage) for the IOC to start gauging the impact and enable a recovery option to begin.)
  • g) Are there parts available at this port?
  • h) Do other airlines have a part that can be used? i) Arc parts and Engineers required to be positioned from another port? (In this case, the aircraft becomes AOG (aircraft on ground), i.e., grounded until rectified.)
  • j) Is the weather conducive to fixing the aircraft on the ramp, or does it need to be towed to a hangar?

Another set of questions addresses different issues, subject to the time of the unserviceability in relation to the scheduled departure time.

  • a) Are the passengers on board? (If the advice received is that passengers are not being boarded, or are being disembarked, the expectation is that a lengthy delay is quite likely.)
  • b) When did the crews (both the Pilots and Flight Attendants) sign on?
  • c) What is the latest sign-off time for these crews?
  • d) If the delay becomes quite protracted, are there replacement crews that could be used?

Quite specific customer-related considerations also need to be addressed.

  • a) Working with the CJM team, are there VIPs/CIPs on board? (The CJM team can then assume responsibility for managing this.)
  • b) What time limitations (normally set by government legislation) apply to the customers remaining on board an aircraft? (After a certain time, legislation may require airlines to de-board an aircraft.)
  • c) Are there customs and immigration facilities available to process customers if de-boarding is required? (This might arise if an aircraft has diverted into a port due to some maintenance issue.)
  • d) Is the airport infrastructure able to cope should customers de-board? (Is there accommodation, transport, food outlets?)
  • e) Are there any special needs customers requiring appropriate attention?
  • f) Are there any unaccompanied minors (who will need appropriate staff supervision/accompaniment) on board?
  • g) Are there any specific freight uplift requirements (e.g. requiring special containment, handling or storage)?

With this information gathered (and keeping in mind that circumstances change, information is updated, and new advice may then alter the state of the problem), the IOC can start to consider options:

a) If the parts are available and the Engineers can fix the aircraft, an initial ETD (estimated time of departure) may be set for the flight.

Nowadays, the digital communications update various airport and other displays as well as passenger hand-held devices, so committing to such times has to reflect a realistic estimate. One difficulty is the opportunity cost that may exist if, having set an ETD, the aircraft becomes serviceable earlier than expected. Either the time would have to be revised to an earlier departure which may be extremely difficult to achieve, or the later ETD has to be respected, with due wastage. This is why an accurate ETS from Engineering is so essential before any advice goes out to the customers. It is also the reason that conservative ETDs are set and may become rolling should rectification take increasingly longer times. In conjunction with Engineering, ideally the aim with regard to an engineering delay is to achieve the published ETS. Timing is crucial to avoid misleading the customers. Underestimating the time and continual revisions result in rolling delays, while overestimating the time wastes opportunities to minimise the disruption.

  • b) Can the problem be isolated to this one flight or at least a small number of flights?
  • c) Can an aircraft swap or some alternative action protect other flights?
  • d) Is there any threat to curfew and, if so, can this be eliminated through similar protection strategies?
  • e) Is there any problem renegotiating new slot times?
  • f) If there are no parts (or licensed Engineers) available and the aircraft becomes AOG, should the flight be delayed or cancelled (if cancelled, what is the best option to accommodate customers on alternate services, either with this airline or with others)?
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