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Less-Than-Lethal Weapons



The Honorable Sarah V. Hart
Director, National Institute of Justice

May 2, 2002
Washington, D.C.

Mr. Chairman and Members of the Subcommittee, I am pleased to appear before the Subcommittee to discuss the work of the National Institute of Justice (NIJ) in developing and testing less-than-lethal weapons for use by commercial airline flight deck crew members in preventing and responding to on-board attackers and potential acts of terrorism. As you know, Mr. Chairman, the Aviation and Transportation Security Act,[1] required NIJ to assess whether less-than-lethal weapons could be used by commercial airline flight deck crew members to temporarily incapacitate persons who present a clear and present danger to the safety of the aircraft, its passengers, or individuals on the ground. That Act required NIJ to submit its findings and recommendations to the Secretary of Transportation. NIJ submitted its report to Transportation Secretary Mineta on April 18, 2002.

As Congress directed, the focus of NIJ’s report was on the use of less-than-lethal weapons in aircraft. As such, NIJ did not undertake an examination of the efficacy of using lethal weapons in a commercial aircraft to thwart an attack. This testimony summarizes the major conclusions and recommendations of NIJ’s report to the Secretary of Transportation.

While our report did discuss countermeasures or other steps that individuals could use to avoid or minimize the effectiveness of the less-than-lethal weapons discussed in this report, for security reasons, that discussion has been omitted from this testimony. I would be pleased, however, to provide this information to the Subcommittee in a closed session.

Moreover, the time constraint -- 90 days from the day the Act became law, or from November 19, 2001 -- set by Congress for NIJ to develop its report did not allow for scientific testing of less-than-lethal weapons in an aircraft setting. Therefore, NIJ prepared its report from information derived from its own research and development of these types of weapons, as well as meetings with experts from the aviation industry and persons experienced in the design and use of less-than-lethal technology in other settings. NIJ’s review of the scientific literature indicated that there are no published formal, scientific test results involving the use of less-than-lethal weapons in a commercial aircraft in flight conditions.

NIJ Less-Than-Lethal Weapons Development Program

Less-than-lethal weapons were developed to provide law enforcement, corrections, and military personnel with an alternative to lethal force. They are designed to temporarily incapacitate, confuse, delay, or restrain an adversary in a variety of situations. They have been used primarily in on-the-street confrontations and suicide interventions, but have also been applied in riots, prison disturbances, and hostage rescues. Less-than-lethal weapons are most often used when: (1) lethal force is not appropriate, (2) lethal force is justified but lesser force may subdue the aggressor, and (3) lethal force is justified but its use could cause collateral effects, such as injury to bystanders or unacceptable damage to property and environment.

Research into less-than-lethal technologies has a long history in the Department of Justice. The first conference on the subject was convened by the Attorney General and the National Science Foundation in 1972. In 1986, then-Attorney General Edwin Meese convened a second national conference on less-than-lethal technologies in response to the U.S. Supreme Court decision Tennessee v. Garner[2], which limited the permissible use of deadly force against felons.[3]

After the 1986 conference, NIJ established a less-than-lethal technologies program. The first research award under this program was made in 1987 to the U.S. Army Chemical Research, Development, and Engineering Center at Aberdeen Proving Ground for a single project -- an assessment of the feasibility of a dart that could deliver a safe but incapacitating chemical to a fleeing suspect. The project evolved to the identification of a candidate chemical and the production of a prototype delivery system. In 1992 NIJ’s program was expanded to include the research, development, modeling, testing, and evaluation of all classes of less-than-lethal weapons to address a wide range of possible applications. Since then, NIJ has invested an average of $1.5 million per year in the program. This year, NIJ will invest $2.5 million in its less-than-lethal program.

Through this program, NIJ seeks technologies that provide new or significantly improved less-than-lethal options to law enforcement and corrections professionals to enable them to reduce the number of deaths and injuries to suspects, prisoners, officers, and bystanders. The program is also designed to evaluate the safety and effectiveness of less-than-lethal weapons through laboratory and field demonstrations, and through the development of computer simulations and mechanical models.

Typically, NIJ-funded projects in this area have focused on:

  • Improving the safety of blunt-trauma projectile weapons;
  • Improving the delivery accuracy and dispersal efficiency of pepper spray for barricade scenarios;
  • Evaluating the safety and effectiveness of pepper spray;
  • Developing and evaluating technology useful for disorienting suspects; and
  • Evaluating the safety and effectiveness of electrical shock weapons.

Use of Less-Than-Lethal Weapons in Commercial Aircraft

Based on its current report, Less-Than-Lethal Weaponry for Aircraft Security, NIJ has concluded that some less-than-lethal weapons, used in accordance with appropriate policies and training, have the potential to allow flight deck crews to thwart an attack in an aircraft. These weapons have the potential to interrupt an attack, control the aggressor, or delay an attack while the flight crew safely lands the plane. However, substantial testing is required before informed decisions can be made as to whether these weapons should be deployed on commercial airlines.

The principal requirements for any less-than-lethal weapon are safety and effectiveness. There is, of course, a natural tension between these two requirements. As the safety of a less-than-lethal weapon is maximized (to protect even the most vulnerable individuals), it degrades the weapon’s ability to incapacitate bigger, stronger, and more determined individuals. Similarly, if effectiveness is maximized (to incapacitate a large adult), then there is a higher risk to a smaller adult or a child. Thus, when the perpetrator’s threat is low, safety becomes the dominant consideration in weapon selection. However, when a perpetrator poses an imminent threat of death or serious harm to others, effectiveness becomes the dominant consideration. In the high-threat situation, safety considerations are pursued if they do not substantially compromise effectiveness.

Aircraft hijackings are high-risk events. As a result, in assessing the appropriate weapons to be used in such a setting, NIJ weighed the balance in favor of effectiveness. This assessment is complicated, however, by the fact that commercial aircraft represent a new environment for the use of less-than-lethal weapons. Most less-than-lethal weapons are designed for use in an open setting or inside a house or other structure, so further testing of these weapons may prove their use inside an aircraft in flight to be impractical.

For example, in commercial aircraft, air is recirculated in relatively small spaces, sensitive critical flight instruments are in continual use, and passenger and crew spaces are crowded and confined. These factors may increase risks to innocent third parties and may increase the likelihood of harming flight crew members or critical aircraft systems. Future substantial testing is required to develop a more complete understanding of the potential adverse effects of less-than-lethal weapons, especially when used in an aircraft under flight conditions.

In developing its assessment for the Secretary of Transportation, NIJ worked closely with representatives of the Federal Aviation Administration (FAA) and experts in the development and use of less-than-lethal weapons to identify the most likely desirable characteristics for a less-than-lethal weapon for flight deck crews. Based on these discussions, NIJ concluded that any less-than-lethal weapon for use on commercial aircraft should:

  • Immediately incapacitate an aggressor. Slow-acting or partially effective weapons may not prevent a determined or trained aggressor from inflicting serious harm to the flight deck crew or critical instruments.
  • Have quickly reversible and controllable effects. If flight crew members are accidentally incapacitated by the weapon, they must be able to return immediately to duty.
  • Be usable in a confined space. Some existing weapons are potentially lethal or ineffective at short ranges. Flight deck crew may be unable to get into an optimal position for operating most existing less-than-lethal weapons.
  • Be simple to operate. A hijacking can evolve rapidly and without warning and flight deck crew must be able to respond immediately and effectively. Extensive training should not be required.
  • Have multi-shot (use) capability. The first shot or application may not completely incapacitate the assailant or there may be multiple assailants.
  • NOT damage critical systems. Damage to critical navigational or environmental systems could endanger the passengers and the flight deck crew.

A Review of Less-Than-Lethal Weapons

There are six general categories of less-than-lethal weapons that currently exist or are in development: electrical shock, chemical, impact projectile, physical restraint, light, and acoustic. No commercially available less-than-lethal weapons have been customized for use on aircraft. In fact, most less-than-lethal weapons are designed for outdoor use. Each of these type of weapons and their potential use in an aircraft setting is discussed below.

Electrical Shock: There are two types of electrical shock devices that have potential use in commercial aircraft. The first is a handheld direct contact weapon that has two probes that are pressed against the skin (or clothing) of an aggressor. When the operator presses a switch, the skin contact and pressed switch complete a circuit, and the subject receives a debilitating and possibly painful electrical shock. The second device, commonly referred to as a dart-firing electrical shocking device, fires two barbs connected to trailing wires that lead back to the operator. When the barbs penetrate the subject’s skin or clothing, an electrical circuit is completed and an electrical discharge (similar to direct contact weapon discharge) automatically results.

One benefit of electrical stun devices is that they produce an immediate incapacitating effect. Direct contact stun weapons can incapacitate an aggressive individual by causing pain and loss of muscle control, but only while contact is maintained. This permits a quick recovery, but requires the user to remain in close and possibly dangerous contact with the aggressor. The incapacitating effect of the dart-firing electrical shocking device can be instantaneous and last for several seconds. This is usually sufficient time to allow the subject to be properly restrained. The dart-firing electrical shocking device also can be reactivated repeatedly if more time is required for restraint or backup.

Once the current flow stops, the subject recovers rapidly (generally in under a minute according to one manufacturer). One benefit of these weapons is that if flight deck crew members were inadvertently incapacitated with an electrical shock device, they could return to duty quickly once the current flow stops.

Another benefit of electrical weapons is that they can be used in a confined space. The maximum range of the direct contact weapon is the length of the arm of the person employing it. The maximum range of the dart-firing electrical shocking device is 15 to 21 feet. The barbs can be discharged at very close range, but the recommended minimum distance is 3 feet, according to the manufacturer. Effectiveness at shorter ranges is not known with any acceptable certainty.

In addition, these weapons are easy to operate. Both the direct contact and the extended range weapons are relatively small and can easily be carried and can be operated with only one hand. Preventive maintenance is critical to ensure that the power source is fully charged or replaced as necessary, and it is likely that the climate controlled environment of an aircraft would be ideal for optimal performance and maximum life of these battery powered devices.

The most important unknown fact about the use of these weapons, however, is the effect such a weapon could have on aircraft avionics or other critical systems. NIJ recommends that electrical discharge weapons not be deployed in aircraft until extensive, independent, and controlled testing has been completed. This testing should be in realistic settings in various types of aircraft to determine the effect that these weapons may have on critical aircraft systems.

Chemical: Chemical less-than-lethal weapons have been used by law enforcement and corrections officers on individuals and crowds. They can range from traditional tear gas to pepper spray to anesthetics or calmatives. Most experts believe tear gas is not likely to be useful in aircraft because its effects generally cannot be adequately controlled in an aircraft cabin. Handheld dispensers of pepper spray offer better control, but still have limitations.

Some very determined and trained aggressors may be able to “work through” the effects of these chemicals. While their ability to move would be affected by these weapons, other means of restraint would be required before the effects of the pepper spray wear off. Also, the effects of these weapons are reversible, but not quickly, a factor that could prove problematic if flight deck crew members were accidentally affected.

Anesthetics or calmative chemicals could, in principle, be developed into a system whereby they could be remotely released into the cabin in order to incapacitate all passengers, and the hijackers, until the plane can be landed safely. Chemical systems of this type have not been employed in the field, however, and remain under study or in development. Also, the effects of these chemicals are not rapid and so may not work fast enough to thwart an attack. Chemical agents used in the cabin may also create unacceptable risks to the health of vulnerable passengers (e.g., infants and those with asthma or other respiratory problems). Finally, the use of these weapons could prevent other passengers from assisting in immobilizing or restraining hijackers.

Impact Projectiles. Many variations of “rubber bullet” impact or blunt trauma projectiles exist. With these weapons, safety concerns from their use at close range are heightened over that of other less-than-lethal weapons. Some of these weapons are relatively safe, even at short distances, and might be adapted for use in an airplane. However, the degree of incapacitation from these weapons varies greatly and the effect can wear off quickly. Moreover, existing versions of these weapons are not designed for use in confined spaces. They typically are launched from a pump-action shotgun or a single round tear gas gun that requires two hands to operate. As such, the weapon is large and not designed to be easily carried on a belt or in a pocket.

Physical Restraints: There are a variety of products that can be used to physically restrain or impede the movement of an aggressor. Although they are not often considered “weapons,” they are often used in conjunction with less-than-lethal devices and so were considered in preparing NIJ’s report to the Secretary of Transportation. These products include nets, surface chemicals, and handcuffs.

Net guns are not practical in the cabin area. Even the remote deployment of a large net covering the cabin would not likely adequately incapacitate a determined and trained hijacker. An electrified net, a design that exists in a prototype (but not specifically for aircraft use), might increase the effectiveness of such a weapon in an aircraft, if it was completely controllable from the cockpit, but effects on aircraft instruments and other performance characteristics is unknown and would have to be tested.

Chemical substances exist that can be applied to surfaces to impede the movement of an aggressor. These substances can be used to make surfaces extremely slippery or extremely sticky, and could be remotely deployed in the cabin area by a flight deck crew member, making it difficult for a hijacker to control his movement on the aircraft floor. Of course, these materials would also affect the other passengers and crew should they come in contact with them, and thus could impede efforts to subdue the hijacker. There is some question as to whether these substances could be deployed with sufficient speed and accuracy to interrupt a fast-paced hijacking.

Handcuffs and flexible cuffs are commonly used physical restraint devices. They should be used in conjunction with any less-than-lethal weapon because these weapons usually produce only a temporary effect. Because it is essential that any potential hijacker or other aggressor be effectively restrained while the plane is landed and security forces arrive, the use of these devices should be part of a overall plan to thwart an attack.

Light: Bright white lights or lasers can produce a “wall of light” that may deter an assailant from attacking someone behind the light. To be truly disabling, however, the light source often requires power levels that may cause eye damage. Even at such a high power level, the device still may not prevent a determined perpetrator from using a weapon. A lower power level “eye-safe” device could be used to distract or delay the advance of the suspect. Such a device could provide sufficient time for passengers and crew to protect themselves or restrain the aggressor. These weapons are still under development by the Department of Defense, with NIJ support.

Acoustics: Acoustic energy, at both audible and inaudible frequencies, has been examined for potential use in less-than-lethal weapons, primarily for halting the advance of an aggressive or violent crowd in a riot scenario. An acoustic source that produces "ear-splitting" audible sounds might be useful as a less-than-lethal weapon under certain circumstances, especially in an indoor environment where some of the technical obstacles are not as serious. These weapons are still under development by the Department of Defense, with NIJ support.


Based on its review of the six less-than-lethal weapon classes, NIJ draws the following conclusions:

  • Electrical shock weapons (both barb-fired and direct contact systems) show the most promise for use by the flight deck crew. However, substantial systematic testing in realistic settings of their effects is essential to ensure they will not damage or disable critical flight systems. This testing must be conducted for each aircraft type in which the weapons may be used.
  • If flight deck crews are armed with any less-than-lethal weapon, handcuffs or other physical restraints should be readily available to incapacitate aggressors until the aircraft can be safely landed and police or security forces can arrive.
  • Impact projectile and physical restraint less-than-lethal weapons should also be considered for use, especially in the aircraft’s cabin, where the restrictions on space are less severe and risks of damage to critical systems or injury to the flight crew are reduced. These weapons could be used as part of a multi-layered defense strategy designed to slow the progress of a hijacker toward the flight deck.
  • Each of these weapon types poses either safety or effectiveness issues that should be tested further in multiple aircraft settings before any deployment. Hence, testing of these products in commercial aircrafts, under conditions that closely approximate the conditions under which they could conceivably be used, should be performed to determine their operational characteristics in such confined spaces and any effects they may cause on aircraft systems. In addition, effectiveness and operational impact reviews need to be completed prior to deploying less-than-lethal weapons on commercial aircraft.
  • Modifications of existing less-than-lethal weapons may be necessary before they can be deployed in aircraft.
  • Light and acoustic weapons need more development, but may eventually be considered for use aboard an aircraft.

I trust these recommendations will be helpful to this Subcommittee, Mr. Chairman, as you work to determine the most effective means of protecting passengers, crew, and property on commercial aircraft. NIJ is committed to continuing to develop the tools that law enforcement needs in order to meet new and emerging threats to our homeland security. As part of this commitment, NIJ will continue its on-going research and development of less-than-lethal weapons, including their possible uses aboard aircraft.

NIJ’s solicitation for applications for research grants in this area for Fiscal Year 2002 has recently closed, and the applications submitted are under review. NIJ has tentatively allocated $1million of its budget for the research grants to be made under this solicitation this fiscal year. In making these grants, NIJ intends to give priority to those applications deemed to be of high quality and that propose to develop less-than-lethal weapons for use in commercial aircraft. In addition, NIJ has committed $1.5 million to further development of ongoing less-than-lethal project. We trust that these research and development efforts will assist this Subcommittee, state and local policy makers, and law enforcement agencies throughout the nation develop effective responses to terrorist attacks on commercial aircraft.


[note 1] Public Law 107-71, Section 126(a).

[note 2] 471 U.S. 1 (1985).

[note 3] That case involved a 15-year-old Memphis boy who was shot and killed in 1974 while fleeing the scene of a $10 burglary. In holding a Tennessee statute unconstitutional, the Court held, “The use of deadly force to prevent the escape of all felony suspects, whatever the circumstances, is constitutionally unreasonable. It is not better that all felony suspects die than that they escape. Where the suspect poses no immediate threat to the officer and no threat to others, the harm resulting from failing to apprehend him does not justify the use of deadly force to do so. A police officer may not seize an unarmed, nondangerous suspect by shooting him dead.” 471 U.S. at 11.