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The second American aid worker diagnosed with Ebola has arrived in Atlanta for treatment, the Associated Press confirms.

Missionary Nancy Writebol, 59, departed from Liberia on Monday in a medical aircraft. She was aboard a plane that landed at Bangor International Airport in Maine just after 8 a.m. EST (1200 GMT) on Tuesday, television station WCSH of Portland, Maine, reported.

The station carried live coverage of the plane stopping to refuel at the airport.

In a statement from Christian missionary group SIM USA released Tuesday afternoon, organization president Bruce Johnson said Writebol is settling in at the medical facility. Her sons, Jeremy and Brian, will be able to visit her. Her husband, David, still remains in Liberia, but will join his wife in Atlanta as soon as he can.

Johnson spoke with David Writebol over the phone earlier Tuesday.

“Nancy is still very, very weak, but shows continued, but slow improvement,” said Johnson. “She is showing signs of progress and moving in the right direction.”

“Nancy had yogurt before getting on the plane,” he said. “When she was put aboard the aircraft about 1 a.m. Monrovia time today, they took her there on a stretcher, but she could stand up and walk with assistance onto the plane.”

“We still have a long way to go, but we have reason to hope,” he said.

Johnson said David Writebol expressed his gratitude for his wife’s return to the U.S.

“Nancy and I are profoundly grateful to the U.S. government and all the machinery that was marshalled on our behalf and what it took to get her home,” said Writebol. “I am very happy. And I am extremely grateful. I am not anxious, fretful or fearful – just relieved.”

“A week ago we were thinking about making funeral arrangements for Nancy,” Writebol continued. “Now we have a real reason to be hopeful.”

Nancy Writebol's arrival came a day after Mount Sinai Hospital in New York City said it was testing a man who traveled to a West African nation where Ebola has been reported. He arrived at the emergency room on Monday with a high fever and a stomach ache, but was in good condition, hospital officials said.

The New York City Health Department, after consulting with the hospital and the U.S. Centers for Disease Control and Prevention, said in a statement on Monday evening that "the patient is unlikely to have Ebola. Specimens are being tested for common causes of illness and to definitively exclude Ebola."

The patient added to concerns about the disease, which has killed nearly 900 people since February and has no proven cure. The death rate in the current epidemic is about 60 percent, experts say.

Writebol will be treated by infectious disease specialists in a special isolation ward at Emory University Hospital in Atlanta, according to Christian missionary group SIM USA.

The mother of two from Charlotte, North Carolina, is a longtime missionary who had been working for SIM USA as a hygienist who decontaminated protective suits worn by healthcare workers inside an isolation unit at a Monrovia treatment center.

Emory's specialists have since Saturday been treating 33-year-old U.S. doctor Kent Brantly, who also returned home after being stricken with Ebola during the emergency response to the worst outbreak on record of the virus.

Writebol and Brantly, believed to be the first Ebola patients ever treated in the United States, served on a joint team in Monrovia run by Christian aid groups SIM USA and Samaritan's Purse. They returned separately because the plane equipped to transport them could carry only one patient at a time.

The pair both saw their conditions improve by varying degrees in Liberia after they received an experimental drug previously tested only on monkeys, a representative for Samaritan's Purse said.

In a statement Tuesday, Brantly's wife, Amber, said she's been able to see her husband daily and that he continues to improve.

"I am thankful for the professionalism and kindness of Dr. Ribner and his team at Emory University Hospital. I know that Kent is receiving the very best medical treatment available," she said. "I am also thrilled to see that Nancy arrived safely in Atlanta today. Our families are united in our faith in Jesus, and we will walk through this recovery time together. Please continue to pray for Kent, Nancy and the people of Liberia."

The Associated Press and Reuters contributed to this report.