American flight crews may be allowed to carry stun guns on airplanes for security reasons, a government agency has concluded in a report.
The Transportation Security Administration (TSA), which has not issued a final decision, said in the classified report to Congress that the guns were an acceptable non-lethal option to deal with hijackers.
"We see electrical shock devices as having the potential to add to our layers of security," TSA spokesman Robert Johnson said.
Congress decided to allow pilots to carry firearms after the 11 September attacks in New York and Washington, despite initial resistance from both the White House and airline companies.
More than 40 US pilots are already flying with handguns after completing a federal training course.
The TSA submitted its report after months of weighing the safety and effectiveness of stun guns, which can immobilise a person for a few seconds by delivering a high voltage shock.
But some experts - including pilots - have said stun guns would hardly be effective in the cramped confines of most flight decks, and instead are favouring lethal firearms.
The agency defended its recommendations, saying the new measure "can provide another deterrent" against terrorists.
"We think they are (stun guns) viable but only viable if done right," Mr Johnson said.
"We're going to be picky about how they deployed and how people have access to them are trained," he added.
The report has been welcomed by some experts in the industry, who say more security options for cabin crews are needed urgently.
"To put defensive capabilities all in the cockpit and not train the crew in the cabin to protect their lives and the lives of the passengers in the event of an attack is unthinkable," spokeswoman for the Association of Flight Attendants Dawn Deeks told Reuters news agency.
Unlike the firearms programme for pilots, stun gun training would not be co-ordinated by the government and would be the responsibility of the airlines.
The TSA prepared its report after two US airlines - United Airlines and the Mesa Air Group had asked the agency to consider allowing their pilots to carry the weapons.
Mr Johnson said that it was possible that pilots could have both firearms and stun guns.