A US Air Force C-130 cargo plane carrying the Americans landed just after midnight (0500 GMT) at Miami International Airport, said a spokesman for the US Southern Command.

After arriving, seven of the eight went to a hotel adjoining the airport.

Ignoring reporters' questions, the group walked briskly through the hotel lobby and got in an elevator as photographers snapped pictures.

Their swift departure from Haiti began a day earlier when Judge Bernard Saint-Vil said eight of the 10 missionaries were free to leave without bail because parents of the children had testified they voluntarily gave their children to the missionaries believing the Americans would give them a better life.

He said, however, that he still wanted to question the group's leader, Laura Silsby, and her former nanny, Charisa Coulter, because they had visited Haiti prior to the quake to inquire about obtaining orphans.

The eight looked tired as they walked out of the Haitian jail escorted by US diplomats on Wednesday evening.

They waited until they were safely inside a white van before flashing smiles to reporters.

Their plane took off from Port-au-Prince shortly thereafter as a group of reporters watched.

The lawyer for nine of the defendants, Aviol Fleurant, said Silsby and Coulter would remain in jail but said the court had not recognised any evidence that they are guilty.

"They are all innocent," he said.

Haitian President Rene Preval told journalists on Wednesday that the judiciary system is handling the situation and is "totally independent."

The missionaries, most from two Baptist churches in Idaho, were charged with child kidnapping for trying to take 33 Haitian children to the Dominican Republic on January 29 without Haitian adoption certificates.

Their detentions came just as aid officials were urging a halt to short-cut adoptions in the wake of the earthquake.

The missionaries say they were on a humanitarian mission to take child quake victims to a hastily prepared orphanage in the Dominican Republic and have denied the trafficking charge.

Silsby originally said they were taking only orphaned and abandoned children, but The Associated Press determined that at least 20 were handed over willingly by their parents, who said the Baptists had promised to educate them and let their parents visit.

Saint-Vil said he did not release Silsby, 47, or Coulter, 24, because of their previous activities in Haiti during a December visit.

Silsby enlisted the rest of the group after the quake.

Coulter, of Boise, Idaho, is diabetic and the judge signed an order on Wednesday afternoon authorising her hospitalisation.

He said he had planned to question both women on Thursday but that Coulter's health situation could prompt a delay.

She had briefly been taken to a US field hospital on Wednesday for treatment after feeling faint but was then taken back to jail.

AP