The top general at the North American Aerospace Defense Command was on the telephone and prepared to order an F-16 fighter to shoot down an unidentified plane that turned out to be carrying the governor of Kentucky to former president Ronald Reagan's funeral last month, according to two federal security officials briefed separately about the incident.

The tense incident June 9 ended after the twin-engine Beechcraft King Air carrying Gov. Ernie Fletcher (R) turned to land at Reagan National Airport. But the close call caused officials to reassess safeguards for the airspace around Washington and prompted calls to expand the no-fly zone beyond its current 16-mile radius.

Although many planes have violated restrictions imposed after the Sept. 11, 2001, terrorist attacks, the June 9 episode was extraordinary because the aircraft penetrated so deeply into the no-fly zone during a high-security event and remained unidentified to air defense officials for several critical minutes. Current and former homeland security officials said the incident was a significant security breakdown.

The episode, described by some officials as the closest the government has come to downing a civilian plane over Washington since Sept. 11, 2001, will be the subject of two hearings on Capitol Hill today. Civil aviation officials will testify before a House subcommittee on aviation, and military officials have been invited to a classified briefing before the House Armed Services and Homeland Security committees.

"Even without the communications breakdowns involved in Governor Fletcher's flight, serious questions remain about the adequacy of our air defense system," said Rep. Jim Turner (Tex.), ranking Democrat on the House Select Committee on Homeland Security. "Does the existing no-fly zone around our nation's capital give sufficient time to intercept a terrorist controlled flight?"

A spokesman for the commander of NORAD, Air Force Gen. Ralph E. "Ed" Eberhart, would not comment on the handling of the incident, saying that rules of engagement are classified. But he and others pointed out that protocols were followed and that the air defense system as a whole is providing unprecedented security.

"The fact that the plane landed without incident June 9 indicates that interagency coordination procedures developed since 9/11 work," said the spokesman, Michael Kucharek.

A reconstruction, based in part on interviews with officials who spoke on condition they not be named, has revealed new details. Senior officials at two federal agencies who are familiar with how the air defense system worked that day said a fighter plane sent to intercept Fletcher's plane initially could not make visual contact because of cloud cover.

As a result, Eberhart did not issue the order to shoot down Fletcher's plane, according to the two officials, as well as a third government official who was briefed later on the incident. Interviews and a timeline prepared by congressional investigators also show that Fletcher's plane turned to land before it was identified.

"They had the general on the phone, and he was in position to make the call. . . . This was the closest we have come to making that difficult decision, triggering a chain of events that could be pretty horrific," one official said.

The air defense system for Washington is unique, and many of its operations are classified. Unveiled in January 2003, the system was created to track all flights and to intercept aircraft that do not follow strict protocols. It replaced the fighter patrols that guarded the nation's capital beginning Sept. 11, 2001, a defense that was costly and did not provide federal authorities with the tools to investigate whether there were patterns in the violations.

The defense system includes a no-fly zone that bars most air traffic from a ring that extends 16 miles from the Washington Monument -- the major exception being commercial flights to and from National Airport. A larger restricted zone, the D.C. Air Defense Identification Zone, extends to about 50 miles from Washington and requires pilots to identify their aircraft, activate identification beacons and stay in two-way radio contact with air controllers.

Immigration and Customs Enforcement helicopters and Cessna jets patrol the zone unarmed, while air defense artillery on the ground and fighter jets on alert or on irregular air patrols are poised to intercept an intruder.

On June 9, the Beechcraft King Air was flying with a broken transponder, a device that transmits an identifying signal picked up by ground controllers. After takeoff, the pilot, as required, notified Federal Aviation Administration officials in Ohio about the problem at 2:56 p.m.

But the FAA failed to notify military and homeland security officials, who monitored separate radar displays, about the broken transponder. To everyone but the FAA, radar showed an unidentified intruder entering restricted Washington airspace at 4:24 p.m.

At 4:31, with the plane a minute or two from downtown Washington, officials ordered the evacuation of the U.S. Capitol, where thousands had gathered to await the arrival of Reagan's coffin. The FAA reported to air defense authorities that it was in contact with the plane three minutes later, as the aircraft made the final approach to National Airport.

The Beechcraft was traveling at roughly 240 miles per hour, or four miles a minute. At that speed, it could have reached the center of the no-fly zone in four minutes.

Customs officials said it took their Black Hawk helicopter four minutes to launch that afternoon, quicker than the designated scramble time. Military fighters happened to be on intermittent air patrols that day, but their standard scramble time from the ground is 15 minutes.

For security officials, a key factor is how little time they had to identify Fletcher's aircraft and make critical decisions. One senior federal security official who has studied the incident said the chances of shooting down the plane would have been "50-50" given the time sequence.

The official said the current system is prepared to stop a second assault, as was the case Sept. 11, not a first attack. Expanding the restricted flight zone -- or a more radical move, such as closing National Airport -- would be required to provide a greater level of security, he said.

Some House investigators are pushing the Transportation Security Administration to improve coordination between a half-dozen agencies. Officials at the TSA and the Pentagon have revived calls for the FAA to expand the restricted flight zones, which would build in more time to make and execute decisions.

Close calls in the past have prompted changes. On June 19, 2002, a Cessna flew over the capital area before it could be intercepted, prompting the evacuation of Vice President Cheney from the White House. Military officials at the time acknowledged that aircraft could reach targets in Washington before they were intercepted by fighters on ground alert.

Authority for air patrols to shoot down a civilian aircraft, once limited to the president, has been delegated to the secretary of defense and his deputy; to Eberhart, as NORAD commander; and to the commander of NORAD's continental U.S. region in Florida, Air Force Maj. Gen. Craig R. McKinley. McKinley has said orders to shoot down aircraft are practiced "probably eight to 15 times a week."

A senior federal security official said the process involved in firing ground-based air defenses operated by the Army or Army National Guard is more complex and needs refinement. Some military officials initially questioned the value of installing short-range missile systems, saying the range and reaction time made their use unlikely.

Customs agents with submachine guns are trained to shoot from the Black Hawks and have authority to use lethal force if their lives or the lives of others are endangered, said Charles E. Stallworth II, director of air and marine operations for Immigration and Customs Enforcement.

Homeland security officials, although aware of limitations, say the system in place is working well and has added layers of protection unavailable on Sept. 11, 2001.

Randy Beardsworth, head of the Department of Homeland Security directorate that includes the TSA and customs enforcement, said advanced radar, computer databases and other tools used by the multi-agency system provide an unprecedented early warning system.

More than 2,000 aircraft "of interest" have been detected over Washington airspace since January 2003, Beardsworth said. The number of aircraft violating the no-fly zone fell from 164 in the six months before Jan. 20, 2003, to 30 after that date through May, 14, 2004.

All 30 intruders were successfully identified, Beardsworth said. By comparison, another federal official said that two years ago, military jets could identify and intercept only about 40 percent of intruders in training drills.

Beardsworth, however, said he does not disagree with those who say the system may not be geared to stop a determined attacker. Like other security officials, he noted that the system's limits are forced by political compromises between security and civilian aviation interests.

Beardsworth said that shooting down hostile aircraft is the responsibility of the Defense Department, not his agency.

"Our role is to help them by having a clear picture when they have to make that tough decision," he said. "Can you imagine how much tougher the decision would be if you didn't have the ability to deter small craft from coming in, if you didn't have the ability to fly out there, detect, identify and deter?"

The plane that carried Kentucky Gov. Ernie Fletcher to Reagan's funeral.