Dealing With Chem/Bio Weapons

What Your Flight Manual Doesn't (Currently) Tell You

Air Line Pilot, July/August 2002, p. 18
By Capt. Bob Hesselbein (Northwest)

You’re cruising along at 35,000 feet when suddenly you learn that a chemical or biological weapon might be on your flight. Or worse, a flight attendant tells you that half the passengers and cabin crew are violently ill without any clear cause, and you suspect a chemical/biological weapon attack on your airplane. What do you do?

According to aviation security experts, the probability of a chemical/biological (chem/bio) weapon being used in an attack against an airliner is real and increasing. These popularly called "weapons of mass destruction" include a variety of liquids and powders designed to cause fatal paralysis, suffocation, blisters, or infection. These agents need not be military grade to be effective; many deadly chemicals can be acquired through commercial sources and used as weapons.

Compared to nuclear devices, chem/bio weapons are relatively inexpensive and simple to produce and, if properly designed, effective. In other words, chem/bio weapons are proven, viable weapons suitable for terrorist organizations seeking to make a mark on world affairs to use. Able to fit into a small container or piece of luggage, a chem/bio device could be smuggled aboard an airplane in carry-on luggage or checked baggage.

With this in mind, what would you do—besides contacting ATC and dispatch—if you were confronted in flight with a valid chem/bio threat to your airplane, passengers, and crew? How is this situation different from dealing with a classic bomb threat?

Aerosol chem/bio activation

Let’s start with a brief explanation of how chem/bio agents could be distributed inside your aircraft: aerosol dispersion. The act of venting, exploding, or manually pouring the substance into the cabin interior will move the agent via simple airborne transmission onto the skin or into the eyes, lungs, and nasal passages. Although the warning that "one drop of nerve gas on your skin will kill you" may be true, aerosol transmission will likely be the primary means of exposure.

With an understanding of the weapon’s likely dispersal characteristics, our goal as crew members will be to contain the weapon’s aerosol potential before it spreads through the cabin, or if unable to do that, to minimize its effect on our passengers and crew.

Some individual flight operations manuals provide useful information on how to deal with explosive devices aboard your airplane; however, a chem/bio risk, because of its very nature, must be dealt with in a somewhat different manner. For example, moving a suspect bomb to the "least risk" location on an aircraft is a great idea, but moving a suspected chem/bio device would be ill-advised.

Dealing with a reported chem/bio threat requires a thought-out plan, good cockpit resource management, and full participation of both cockpit and cabin crew.

Determining the location of the suspected device, identifying the exact threat, and deciding on the appropriate reaction to the threat require calm thinking, clear communication, and a cautious, timely response.

All crew members must be involved, but separating responsibilities between the cockpit and cabin is important. The cockpit crew must focus on flying the airplane and managing the cabin temperature, pressurization, and other systems while coordinating with dispatch and any agencies that may be helping.

The flight attendants, on the other hand, should deal with any suspected chem/bio device in the cabin while carrying out their appropriate emergency prelanding procedures.

The correct crew reaction will depend on the location and status of a chem/bio weapon. The specific threat situation and response must be separated into categories of location (cabin versus cargo area) and condition (unactivated versus activated weapon).

Cabin threats without activation

If a chem/bio device is reported on the airplane (but without apparent activation because no one has reported any symptoms), the crew must take immediate steps to deal with the situation and try to minimize aerosol dispersion immediately.

Cockpit and cabin crewmembers have different duties that should be started simultaneously.

Cockpit crewmembers should immediately don masks and goggles, select 100 percent oxygen, and maximize their skin protection by keeping their shirtsleeves down or wearing their uniform jackets. Although declaring an emergency and turning toward a diversion airport are appropriate, the flight crew should not change the cabin pressure until the unactivated device has been secured to the maximum extent possible.

Immediately reducing cabin temperature to the lowest practical setting and turning off recirculation fans will decrease most aerosol dispersion characteristics.

Cabin crewmembers should also don uniform jackets and prepare to seek out the suspected device. If time permits, flight attendants should give the passengers moistened paper towels to be used as emergency breathing filters (surprisingly, they actually help filter certain gases).

If the chem/bio device is reported to be in a specific piece of luggage or location, the cabin crew should identify the device without moving or touching it.

After the device is identified, all passengers should be removed from the immediate area while steps are taken to isolate and seal the weapon as much as possible. Cabin crewmembers should prepare for isolating the device by covering all of their exposed skin and donning rubber gloves and personal breathing equipment.

Securing a suspected chem/bio weapon

Blocking the weapon’s ability to disperse a chemical or biological agent in the cabin is of paramount importance.

Remove all items surrounding the container/luggage holding the suspected chem/bio device, but do not move the suspected device! Instead, cover and seal the device as much as possible with layers of plastic trash bags, dry blankets, more plastic, wet blankets, and then more dry blankets. Create as many barrier layers as possible between the agent and the cabin atmosphere.

Remember: the primary goal is to contain the chemical or biological agent and keep it out of the cabin atmosphere.

After the suspected chem/bio container is covered and sealed from the cabin atmosphere, start a gradual descent at a rate that minimizes the rate of increase in cabin pressure. The slower the descent and the increase in cabin pressure, the lower the risk of agent dispersal during the final phase of flight.

After landing and taxiing to the airport minimum-risk location, park diagonal to the surface winds to minimize passenger risk of contamination while deplaning through the airplane’s upwind exits.

Even if no manifestation of possible chem/bio contamination is apparent, passengers and crew should remain together and quarantined until they are checked by trained personnel.

Cabin threats with activation

Unexpected exposure to an activated chem/bio weapon within the confines of an aircraft cabin is one of the worst possible situations imaginable. Survival will require quick identification, clear thinking, and swift response.

With the exception of slow-acting biological agents such as anthrax, airborne exposure will rapidly generate sudden passenger sickness in an epidemic outbreak. Depending on the agent, passengers and cabin crew may exhibit choking, skin discoloration, and fainting, blistering, or convulsions that are beyond the means of crew members to treat effectively while airborne.

When this situation is reported to the flight crew, the cockpit crewmembers must immediately don masks and goggles, secure the cabin door, and deny entry from the cabin.

Next, decrease cabin pressure (by raising the cabin altitude) as quickly as possible—and as much as possible—to evacuate and dilute the aerosol agent.

Additionally, turn off recirculation fans and select the coldest possible cabin temperature to help minimize aerosol dispersion.

Descending rapidly and diverting to a suitable airport are critically important. Land immediately to ensure that cockpit crewmembers are physically able to land the airplane and to get time-critical medical treatment for exposed individuals.

Don’t hesitate to land at a major airport because of fear of contaminating large populated areas, as chemical agents generally are effective for only a short time and will dissipate rapidly. Get the airplane on the ground while you can!

Cargo compartment threats

A reported chem/bio threat in a cargo compartment should be dealt with much as one would deal with a cargo fire. Isolate the cargo bay by removing all sources of ventilation and shut off cargo heat sources and recirculation fans. These steps will significantly restrict agent dispersion and help protect the passenger cabin.

Smoke detectors in the cargo hold may sense inflight activation of a chem/bio weapon. You can’t tell from illuminated warning lights whether the smoke is from a weapon or cargo fire, but normal firefighting techniques will provide optimal protection while airborne.

During descent, a positive outflow of pressure from the packs will decrease the risk of chemical or biological agents migrating from the cargo bays into the cabin. To sustain this protection until a planned deplaning, setting the landing elevation somewhat lower than the actual destination will keep the cabin relatively overpressurized throughout the landing phase of flight. Depending on the airplane, time, and system knowledge, manually keeping outflow valves from fully opening upon landing could keep the cabin overpressurized and protected from cargo area contamination until the passengers and crew are ready to evacuate through upwind exits.

Diverting and deplaning

If possible, coordinate through ATC and dispatch to land at an airport that has explosive, chem/bio, and medical experts waiting to help you with deplaning and, if necessary, decontamination. Coordinating your actions with local emergency response agencies to the maximum extent possible is critically important. You are sitting in a potentially deadly threat that is also a threat to those outside your airplane.

If confusion and miscommunication reign outside the cockpit, you can take certain steps to minimize the risk to the airport and surrounding communities. First, try to avoid flying over populated areas during the approach and landing. Second, after landing, do not taxi to a terminal; instead, seek a location downwind of populated structures. Third, park diagonal to reported winds and allow deplaning only on the upwind side of the airplane. Finally, keep all passengers and crew together and quarantined from nonemergency personnel.


No general article on the complex subject of dealing with chem/bio weapons in flight can provide the information and techniques appropriate for each specific aircraft type —and I certainly do not intend to suggest otherwise. The sole purpose of my writing this is to get you, the crew member, to consider in advance how you would deal with a genuine chem/bio threat in your airplane.

Events of the past clearly demonstrate that the unexpected and unthinkable should be expected—and planned for accordingly. Encountering a chem/bio weapon on your flight is unlikely, but possible. With a bit of thinking about the possibility, and preplanning a response, a chem/bio attack is survivable.

Capt. Bob Hesselbein is a member of the Northwest pilots’ Master Executive Council Security Committee.

Supplement 1: Procedure Matrix
Situation:     Cabin Unactivated     Cabin Activated     Cargo Hold
Crew Action:     • Don mask and goggles     • Don mask and goggles     • Don mask and goggles
  • Inform ATC and declare emergency    • Inform ATC and declare emergency    • Inform ATC and declare emergency
  • Do not change altitude until procedure directs    • Turn off recirculation fans    • Turn off recirculation fans
  • Turn off recirculation fans    • Raise cabin altitude to 10,000 feet at fastest rate possible    • Follow cargo smoke/fire checklist
  • Decrease cabin temperature     • Decrease cabin temperature     • Advise SOC
  • Attempt to contain/wrap device     • Follow Emergency Descent Procedure     • Maintain positive cabin pressure until landing
  • Advise SOC     • Advise SOC     • Stop airplane with surface wind at 10/2 o’clock position
  • Start slow descent to appropriate divert airport • After landing, evacuate via upwind side of airplane    • After landing, evacuate via upwind side of airplane
  • Quarantine passengers upwind of airplane until help arrives    • Quarantine passengers upwind of airplane until help arrives • Quarantine passengers upwind of airplane until help arrives



Supplement 2: 
Captain Considerations Upon Landing

Since Sept. 11, 2001, ground emergency response procedures have improved nationwide and now include dealing with chem/bio threats. Response procedures for dealing with airplanes, however, are still evolving. Depending on the location, the procedures may not adequately address the issue of dealing with airplanes full of chemically or biologically contaminated and injured passengers. In many cases, local response teams may direct the airplane to a remote location and await chemical tests of the exterior, etc., before directing the crew to evacuate the airplane.

In a life-and-death situation, the captain and crew will have the best situational awareness of cabin conditions and must make the decision to evacuate or not. If the chem/bio agent is a relatively benign, slow-acting substance such as anthrax spores, remaining inside the airplane is appropriate until directed to evacuate. If the agent is aggressive and causing immediate injuries and death, the captain must decide to override outside instructions and begin an emergency evacuation. This is a critical decision that can save lives.

A captain who decides to order an emergency evacuation out the upwind side of the airplane should advise ground emergency personnel of his or her intentions. This will allow emergency responders to reposition and provide whatever help is possible.

During and after evacuation, containing crew and passengers in a small quarantine area upwind of the aircraft until appropriate ground staff is available to determine the nature of the chem/bio agent and the appropriate medical assistance is of paramount importance. This is critical because exposed individuals can contaminate others, depending on the particular chem/bio threat.