The Air Force dropped homicide and assault charges Thursday against two fighter pilots who mistakenly bombed Canadian soldiers in Afghanistan last year, killing four.

The pilots, Majs. Harry Schmidt (search) and William Umbach (search), had been charged with involuntary manslaughter, aggravated assault and dereliction of duty and faced up to 64 years in prison if convicted in a court-martial.

The decision was met with disappointment by relatives of the Canadian soldiers.

"I was hoping ... for a court-martial," said Marley Leger, wife of Sgt. Marc Leger, who died when the powerful explosive detonated next to him. But "it doesn't matter what the decision would be. It would not bring back Marc."

Lt. Gen. Bruce Carlson (search), commander of the Louisiana-based 8th Air Force, dropped all charges against Umbach. Schmidt still faces dereliction of duty counts but will not be court-martialed.

Carlson recommended that commanders should decide whether Schmidt, who released the 500-pound bomb from an F-16 (search), should be punished for lesser criminal offenses, including failure to ensure that the troops he attacked were not allies and to obey when air controllers told him to "stand by" before he dropped the bomb.

Carlson also recommended that a flying evaluation board determine whether Schmidt should be allowed to fly for the Air Force again. The maximum non-judicial punishment would be a reprimand, forfeiture of a month's pay, confinement to quarters for a month and restriction on travel for two months.

Schmidt could refuse the non-judicial hearing and insist on a trial. His defense lawyer, Charles Gittins, said Thursday the pilot was considering his options.

"Like the other 14 friendly fire accidents that have occurred in Iraq and Afghanistan, charges should not have been pursued in the first place," Gittins said.

Umbach, the mission commander, was issued a letter of reprimand for "leadership failures." He had asked to retire, and the general recommended it be approved.

Both pilots declined to comment.

The two Illinois Air National Guardsmen had been the first Air Force pilots to face homicide charges as a result of a friendly fire incident during combat.

Schmidt, 37, blamed the "fog of war" for the mistake, saying he believed he and Umbach, 44, were being ambushed by ground forces.

The pilots said they were never told the Canadians would be conducting live-ammunition exercises that night. Defense attorneys suggested Air Force-issued amphetamines, which were routine issued to help aviators stay awake during long missions, had clouded the pilots' judgment. They also blamed a military communications breakdown and said Air Force brass, not the pilots, should be punished.

A joint U.S.-Canadian investigation into the bombing concluded that the pilots were at fault for the Canadian soldiers' deaths, and the head of the probe said they showed "reckless disregard" for standing orders against attacking, ignored briefings about allied troop locations and should have simply flown out of the area.

But an Air Force judge who presided over a military hearing in January recommended all criminal charges be dropped and that the pilots instead face internal Air Force discipline. Carlson followed that recommendation.

The case had been closely watched in Canada, where many were outraged by the bombing and the two days it took President Bush to publicly apologize.

Canada's defense chief, Ray Henault, responded to the announcement Thursday, saying: "While risk is an inherent part of military operations, we will continue to work with our allies to mitigate the possibility of such a tragedy recurring."

He said Canada would remain committed to contributing to international peace and security.

Besides Leger, the April 17, 2002, bombing near Kandahar killed Pvt. Richard Green, Cpl. Ainsworth Dyer and Pvt. Nathan Smith and Sgt. Marc and wounded eight other Canadians. They were the first Canadians to die in combat since the Korean War.

Schmidt and Umbach had been returning from a 10-hour patrol, at more than 15,000 feet, when they spotted surface-to-air fire. It turned out to be from Canadians with the 3rd Battalion of the Princess Patricia's Canadian Light Infantry, based near Edmonton.

The Canadians were firing rounds horizontally, not vertically in a way that would have threatened the two F-16s, according to investigators. The bomb was dropped despite a flight controller telling Schmidt to "hold fire."

Less than three minutes after the bomb hit, Schmidt said: "I hope that was the right thing to do," according to recordings of the mission.

"Me too," said Umbach, the mission's commander.

Schmidt had transferred to the National Guard in 2000 after a decorated career as a Navy pilot and an instructor at the Navy's "Top Gun" fighter pilot school. Umbach is a United Airlines pilot who had served in the Air Force.