"Our role was top simply to pass on information," Mr. Bush said at a news conference closing out the Summit of the Americas.
On Friday, the Peruvian air force shot down the missionaries' Cessna 185 single-engine plane, which was mistakenly identified as the carrier of illegal drugs.
Baptist missionary Veronica "Roni" Bowers and her 7-month-old adopted daughter, Charity, the pilot wounded. Her husband and son survived.
CBS News Correspondent Lee Cowan reports there are serious questions inside the U.S. government about how such a deadly mistake could happen: How could a private plane carrying 5 Americans missionaries, be shot out of the sky by Peruvian fighter jets, after being identified, even tracked for the Peruvians, by a U.S. government surveillance plane?
"Our government is involved with helping, and a variety of agencies are involved with helping, our friends in South America identify airplanes that might be carrying illegal drugs," Mr. Bush said. "These operations have been going on for quite a while."
He added that such flights have been suspended "until we get to the bottom of the situation, to fully understand all the facts, to understand what went wrong in this terrible tragedy."
A U.S. surveillance plane was tracking the missionaries' plane before it was shot down and had been in communication with the Peruvian air force, American officials have said.
"Our role was to, like in other missions, was to provide information as to tail numbers," Mr. Bush said. "Our role is to help identify planes that fail to file flight plans."
The Peruvian government has said the plane entered Peruvian air space from Brazil without filing a flight plan. Airport officials have said the plane did not have a flight plan when it set out from Islandia, next to Brazil's border, Friday morning, but one was established when the pilot made radio contact with Iquitos' airport control tower.
The pilot's father says he saw a copy of his son's flight plan so did the plane's mechanic. The pilot's brother says it's the only way he would have flown.
"Having been flying down there for 13 years now, he certainly knows the government, he knows how they operate, he knows what the procedures are," said pilot Donaldson's brother Gordon.
CBS News has been told the pilot also radioed his position to the airport tower minutes before he was to land. In that part of Peru, the tower operator told CBS, that's as good as any other a flight plan.
"Our hearts go out to the families who have been affected," the president said. "I want everybody in my country to understand that we weep for the families whose lives have been affected."
CBS News Correspondnt Jim Krasula reports Jim Bowers arrived at Raleigh-Durham International airport in North Carolina midday Sunday with his 7-year old son Cory and his brother Phil.
The Bowers were on a mission sponsored by the Association of Baptists for World Evangelism based in New Cumberland, Penns. In a written statement, the group asks that the media allow the Bowers' family privacy to grieve together.
Pilot Kevin Donaldson was very experienced, says the association, and both he and his plane were well known to Peruvian authorities, says E.C. Haskell, a spokesman for the Association of Baptists for World Evangelism (ABWE), adding, "No way this should have happened."
Between 1994 and 1997, Peru shot down about 25 suspected drug planes on their way to Colombian cocaine refineries from coca-growing regions in Peru's Amazon.
The actions were the result of former President Alberto Fujimori's tough anti-narcotics policies in an effort to reducing trafficking in coca leaf, the raw material used to make cocaine.
In July, Fujimori said the country would use its fleet of 18 Russian-made Sukhoi-25 fighter jets in the anti-drug fight. The planes were originally bought after a brief border war with Ecuador in 1995.
Haskell said Kevin Donaldson grew up in Peru. Their group runs a theological seminary, schools, a camp and a center for pregnant women.
The Bowers family is from Muskegon, Michigan, and Donaldson from Morgantown, Pennsylvania, said Haskell.
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