A military hearing officer recommended Thursday that charges be dismissed against two U.S. pilots who mistakenly dropped a bomb in Afghanistan last spring, killing four Canadian soldiers conducting live-fire exercises.

Col. Patrick Rosenow said that although there was enough evidence to court-martial the two, internal Air Force penalties would maintain "the interests of good order and discipline."

Rosenow presided over the investigative hearing in Louisiana in January. His recommendation will be key in determining whether Majs. Harry Schmidt and William Umbach will face a military trial on the involuntary manslaughter and other charges that could put each of them in prison for up to 64 years.

The final decision is up to Lt. Gen. Bruce Carlson, commander of the 8th Air Force. There was no immediate indication when Carlson might rule.

If there is no court-martial, Air Force spokeswoman Capt. Denise Kerr said disciplinary action could include a written reprimand, discharge or the loss of two months' pay.

Schmidt declined to comment on the recommendation. His mother, Joan Schmidt, said she was relieved. "It's absolutely wonderful and I'm grateful and I'm thankful," she said from her Missouri home.

Umbach's lawyer, David Beck, didn't return calls for comment.

Some relatives of the Canadian soldiers criticized the recommendation.

"This is just a charade. They just get away with murder," said Agatha Dyer, whose son, Cpl. Ainsworth Dyer, died in the bombing.

Canadian Defense Minister John McCallum declined to comment.

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. The bomb also wounded eight other Canadians.

The Air Force did not release Rosenow's entire report. But according to Charles Gittins, Schmidt's lawyer, Rosenow reasoned the Air Force would have difficulty disproving the pilots' main defense: that Schmidt attacked because he believed the enemy was attacking from the ground.

Schmidt and Umbach, of the Illinois Air National Guard, said they had never been told allied troops might be holding exercises in the area last April 17.

Schmidt, who dropped the bomb, blamed the "fog of war" and said he believed he and Umbach had been ambushed. Defense attorneys also suggested Air Force-issued amphetamines had clouded the pilots' judgment.

A joint U.S.-Canadian investigation concluded the pilots were to blame. The head of the investigation testified the men showed "reckless disregard."

Schmidt and Umbach became the first Air Force pilots to face homicide charges as a result of combat when they were charged with manslaughter, aggravated assault and dereliction of duty.

The pilots were returning from a 10-hour patrol, at more than 15,000 feet, when they spotted surface-to-air fire and feared it was from Taliban forces. It turned out to be from Canadians with the 3rd Battalion of the Princess Patricia's Canadian Light Infantry, based near Edmonton.

The troops were near Kandahar at a practice range. The Canadians were firing rounds horizontally, not vertically in a way that would have threatened the two F-16s, according to investigators.

On audio and video taken from Schmidt's F-16, a flight controller is heard saying "hold fire" after Schmidt asks permission to fire his cannons, thinking Umbach was under attack.

Four seconds later, Schmidt said he was "rolling in, in self defense." The laser-guided bomb he dropped killed Dyer, Sgt. Marc Leger, Pvt. Richard Green and Pvt. Nathan Smith.

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

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

Schmidt transferred to the National Guard in 2000 after a combat-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.

At the hearing, several F-16 pilots said Schmidt and Umbach had done nothing wrong because airmen are trained to attack if they believe they are under enemy fire.

Defense lawyers cast the men as scapegoats for a military communications breakdown, and said Air Force brass, not the pilots, should be punished.