Radiation Cloud: Guidance for Flight Crews

Radiation Cloud: Guidance for Flight Crews


If the aircraft encounters radioactive material, either in-flight or while on the ground, flight crews should follow company approved emergency procedures and manufacturers guidance regarding the conduct of the flight, and management of aircraft systems

Dealing with a situation that has already occurred and for which avoidance plans have been put in place may be relatively straightforward. However, dealing with an unexpected situation that happens in flight would be more difficult to manage. Crews and operators who have spent some time ‘thinking the unthinkable’ before such an event will invariably be better prepared.

NOTE: Issues relating to exposure to naturally occurring radiation at high altitudes are covered in a separate article on Cosmic Radiation.


This article considers some of the airmanship aspects , which are applicable generically to all aircraft and situations, relating to an encounter with radioactive material in flight or while on the ground. It does not provide guidance on decontamination or the handling of radioactive cargo.

References sometimes use the term "radioactive cloud" is sometimes made in references. In this context, the term "cloud" means a contaminated volume of air and is not necessarily associated with moisture. As with ash clouds (see Volcanic Ash and Pyrocumulus), there are no physical or visible boundaries to the contaminated volumes, only arbitrary borderlines denoting when the contamination is deemed to be significant.


Pre-Flight Planning

NOTAM should be published whenever an atmospheric release of radioactive materials or toxic chemicals has occurred following a nuclear or chemical incident.

Meteorological offices, and the Volcanic Ash Advisory Centre (VAAC) for the affected region, may provide forecasts for the movement of the material, for example on SIGMET charts, to enable forward planning of schedules to avoid any radioactive material in flight and fall-out of radioactive material.

Operators should ensure that crews are aware of relevant NOTAMs and monitor developments. Routes should be planned taking into account the notified location of dispersing radioactive material.

Where a flight has been planned to avoid such contamination, crews should consider the possibility that further in flight re-routing may become necessary. Commanders should give careful consideration to extra fuel requirements and the facilities at potential diversion airfields, including their capability to help deal with any actual or potential contamination of the aircraft, crew and passengers including medical support.

In-Flight Avoidance

ATC may be able to provide crews with updated information on the location of radioactive material and offer avoiding action. In certain circumstances, a diversion may be warranted.

Indications and In-Flight Effects

Unless an aircraft is fitted with specific monitoring equipment, crews are unlikely to detect the presence of radioactive material in the atmosphere. Even in the extreme case where aircraft systems might be affected by the electromagnetic pulse from a nuclear explosion, that in itself would not indicate the presence of radioactive material in the vicinity of the aircraft.

Furthermore, if an aircraft does encounter a cloud of radioactive material following a nuclear incident or accident, the aircrew and passengers would be unlikely to be affected immediately. Therefore, the aircrew would not be incapacitated and could complete the flight safely.

Actions in Flight

If there are reasons to believe that the aircraft may be flying through, or at risk of flying through, radioactive material, the following actions may be prudent:

  • Cabin Air. Minimise intake of contaminated air from outside the aircraft as much as possible. The ideal would be to prevent all external air from entering the cabin. The crew must have a clear understanding of how the air conditioning and pressurisation system works on their aircraft so that, together with company and manufacturers’ recommendations, they can decide how best to configure the system.
  • 100% Oxygen. Use of flight crew oxygen masks, with 100% Oxygen selected, will reduce the likelihood of ingestion of airborne radioactive particles. Use of oxygen in such circumstance may leave insufficient to cater for more routine incidents such as fire or decompression and the height of terrain over which the flight will be conducted may be a further consideration. At the planning stage, potential use of oxygen and the consequent reduction in oxygen endurance will have a major impact on which route might be appropriate to avoid an area of known contamination.


Flight through precipitation from contaminated clouds, or flight within volumes of contaminated air, is likely to lead to deposition of contaminated particles on the airframe. Such depositions may remain after landing in areas not directly exposed to airflow effects.

Useful practical guidelines relating to decontamination have been issued by the AEA:

  • AEA Guidelines on Radioactive Contamination of Aircraft and Engines, 3rd Edition, June 2002. Company advice should be available on the actions to take in the event of suspected contamination. In the absence of such advice being available before flight, commanders may wish to consider the wisdom of flying through an area where there is potential for contamination to occur. Note also that once on the ground, local authorities may well take over decontamination procedures, possibly also removing control from the aircraft commander; this would need careful handling and management to safeguard the best interests of passengers and crew

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