VILLAVICENCIO, Colombia (CNN) -- -- Two Venezuelan helicopters arrived in central Colombia on Friday as part of an operation to free three hostages from the jungles of Colombia.
President Hugo Chavez of Venezuela organized the operation to free hostages who have endured several years of captivity.
Chavez reached a deal with their captors, the leftist Revolutionary Armed Forces of Colombia, or FARC, the Spanish acronym by which the rebel group is known.
Chavez wore an olive drab military uniform and red beret as he watched the helicopters take off on their journey to Colombia. The helicopters carried the symbol of the International Committee of the Red Cross.
The helicopters flew to the central Colombian city of Villavicencio. Other aircraft plan to follow. 
Watch a report detailing the mission »
The helicopters and airplanes will refuel in Villavicencio and wait for the FARC to direct the Venezuelans to a location in the Colombian jungle, where the rebels will relinquish custody of the hostages.
The aircraft are to then take the freed hostages to Villavicencio or one of several airports in Venezuela, depending on the location of the pickup site.
Three Venezuelan airplanes and two helicopters will carry medics and dignitaries from Venezuela to Colombia, said Luis Carlos Restrepo, the Colombian peace negotiator.
"We hope that all goes according to plan," he told reporters Friday. "We have been in constant communication with the Venezuelan government."
He said the Colombian authorities have "given all necessary guarantees" to ensure the mission's success, an apparent reference to Colombia's pledge not to pursue the rebels during the scheduled hostage handover.
About 100 indigenous Colombians, who live in the jungle, are on standby in a jungle town in the event of a problem with the helicopters, said Jorge Diaz, who is in charge of Colombian civil defense in the region around Villavicencio.
They could travel deep into the jungle on foot should the operation encounter unexpected difficulty, such as a mechanical problem with one of the helicopters, he said.
It's unclear when the hostages will actually be free, but the Colombian government has set a tentative deadline of 7 p.m. Sunday (11.30 p.m. GMT) for the mission to be complete.
The hostages to be freed include Clara Rojas, who was kidnapped in 2002 while she managed the campaign of Sen. Ingrid Betancourt, a candidate for the Colombian presidency. They also include Rojas' son, Emmanuel, who was born in captivity, and Consuelo Gonzalez, a former Colombian congressman.
Betancourt herself is perhaps the best-known captive in a country plagued by kidnapping.
The FARC holds her and dozens of other hostages, including three defense contractors from the United States who were seized after their plane crashed in 2003.
It has justified hostage-taking as a legitimate military tactic in a long-running and complex civil war that also has involved right-wing paramilitaries, government forces and drug traffickers. The fighting has waned but not stopped in recent years.
News of the planned release has stirred hope that the FARC could free others in captivity. Chavez said this week that he hopes the three hostages will be the first of several to be released.
Patricia Perdomo, daughter of Gonzales, told reporters in Caracas on Thursday that she views her mother's impending freedom as a sign of things to come.
"This sign that the FARC is giving us is very, very, very important because it opens the door for other hostages who are not returning now but who will return home one day," she said. E-mail to a friend 
CNN's Karl Penhaul contributed to this report
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