Yesterday's shooting death of American Airlines passenger Rigoberto Alpizar at Miami International Airport by a federal air marshal was cited by some congressional leaders and air security experts as the first successful -- if deadly -- example of the government's ramped-up commercial airline security efforts.

But others said that opening fire on passengers who threaten airline travel could lead to even worse consequences for bystanders.

"This shows that the program has worked beyond our expectations," said Rep. John L. Mica (R-Fla.), chairman of the House transportation subcommittee on aviation. "This should send a message to a terrorist or anyone else who is considering disrupting an aircraft with a threat."

Before yesterday's shooting, Mica said there remained further debate in Washington on whether the program should be expanded. But some security experts question whether killing the passenger, whose wife, according to other passengers, said was mentally troubled , was justified

Federal air marshals are not trained to negotiate with suspected terrorists, Mica said, especially passengers who claim they are carrying an explosive device, as Alpizar said yesterday. Mica said the marshal acted appropriately.

"Air marshals don't have time for counseling or interviewing passengers. They have to make split-second decisions based on the current threat," Mica said.

In the weeks following the Sept. 11, 2001, terrorist attacks, numerous lawmakers and airline industry officials participated in congressional hearings that led to expanding the federal air marshal program through additional hiring and training.

At that time, there were 33 air marshals monitoring about 30,000 domestic flights a day. Now, after the congressional push, several thousand marshals ride on domestic and international flights.

Aviation security consultant Douglas R. Laird of Laird & Associates said shooting a suspect who claims to be carrying an explosive device could cause a greater threat to passengers if that suspect detonates the bomb after being shot. "It's a terrible call," the former Northwest Airlines security director said.

The shooting yesterday was another example of why the air marshal program should be expanded through additional training and staffing, said Jon Adler, national executive vice president of the Federal Law Enforcement Officers Association, an organization made up of 24,000 law enforcement officers, including 1,300 air marshals.

Adler said that after the Sept. 11 attacks, a greater emphasis was placed on defensive tactics and marksmanship in air marshal training. Although Adler said the marshal in yesterday's shooting acted "appropriately," he added that greater training is necessary. "It's a continued effort," Adler said.

Additional training and hiring means the need for more funding. The program is currently under the Transportation Security Administration, which is part of the Homeland Security Department. Last month, a study by the Government Accountability Office reported that efforts to expand the marshal program was abandoned more than a year ago because of costs. At the time, an effort was underway to train thousands of customs and immigration agents to serve as federal marshals during heightened terror alerts.

One aspect of expanding the air marshal program includes whether the marshals should be armed with weapons other than guns.

Before filing for bankruptcy protection three years ago, United Airlines tested whether to arm pilots and air marshals with Tasers -- high-voltage stun guns -- as opposed to firearms. United's pilot program was abandoned when the airline filed for bankruptcy, said Tom Smith, president of Taser International Inc. The airline determined that it would cost $700,000 to equip all of its planes with two Tasers. Airlines never received government permission to put Tasers on board aircraft.

In September, security officials used a Taser to subdue a man who breached airport security at Manchester Airport in England and was able to flee onto the airport's tarmac.