In the latest move to improve safety in the skies, United Airlines on Thursday became the first major carrier to announce plans to install stun guns in the cockpits of all its planes.

United also said it is starting a special training program for flight attendants, aimed at both self-protection and assisting passengers.

Both measures are subject to federal government approval.

Pending that, the nation's second-biggest carrier said it will soon start installing advanced Taser stun guns in electronically coded lock boxes in all planes, enabling pilots to fend off hijacking attempts.

The weapons fire an electronic charge that disables an attacker for five seconds or more, allowing time for them to be restrained. Pilots will be trained in how to use the devices.

"United and its pilots believe Tasers are an important addition to enhanced cockpit security. Tasers will incapacitate an attacker without endangering the airplane," said United CEO Andrew Studdert.

United declined to discuss specifics of the new training program for flight attendants, indicating that it could compromise the program's effectiveness.

Since the Sept. 11 terrorist attacks, airlines have been taking security matters into their own hands. Most have been reinforcing cockpit doors with iron bars. Among other measures, Austrian Airlines put armed sky marshals on board all its flights to and from North America and carriers have even considered arming pilots with hand guns.

The Federal Aviation Administration has been reviewing its rule prohibiting any deadly or dangerous weapon on scheduled passenger flights. Congress, which has been working to tighten airline security since the attacks, also could override it.

Other airlines besides United also have been considering stun guns. Mesa Air Group, which operates America West Express and US Airways Express, announced last month it planned to train its pilots to use them, and the manufacturer of Tasers, Scottsdale, Ariz.-based Taser International Inc., has held discussions with several carriers.

Using a laser sight, the Taser shoots a pair of quarter-inch darts trailing wires into the attacker. A five-second, 26-watt shot of electricity contracts the muscles and overwhelms the central nervous system, preventing any coordinated action. The weapons can take down a hijacker from 21 feet away, according to the manufacturer.

United pilot Herb Hunter, a spokesman for the Air Line Pilots Association, endorsed the stun-gun plan as "a good first step."

"We have supported a three-pronged approach: Keep the bad guys off the jets, strengthen and eventually replace the cockpit doors and put defensive systems for pilots in the cockpit," Hunter said.

"Is this a panacea? No. But it's certainly a move in the right direction, and we support it."