They met last year at 35,000 feet, on a cramped, red-eye flight from Los Angeles to Baltimore.
He is a former emergency medical technician from Frederick, who got up when no other passenger responded to a public-address query, "Is there a doctor on the plane?"
She was the passenger who prompted the message: a seemingly fit woman from Columbia who was suddenly awakened by sharp back pains that soon made it difficult to breathe.
At the time, neither Jim Addington nor Erin McKelvey realized that she was moments away from succumbing to a pulmonary embolism, a life-threatening complication in which blood clots block an artery in the lung. He only knew that something was terribly wrong and that the flight needed to be diverted so she could receive medical attention.
Addington's decision not only likely saved McKelvey's life but changed it. "It has certainly made me a better mother and more in tune to the fact that time is not guaranteed, McKelvey said.
For his heroics, Addington will be among 40 people honored June 19 in Washington with this year's Vita Wireless Samaritan Award, a nonmonetary prize given by the Cellular Telecommunications Industry Association for people who use wireless technology in an emergency.
"I think [the award] is pretty exciting, and it's humbling," said Addington, "because I didn't feel I did anything special. I now recognize the impact of what I did, and I would do it again without any thought."
But beyond the award, the encounter produced a friendship. It took McKelvey nearly a year to track Addington down, but to see their easy camaraderie when they met at a Columbia restaurant recently, you would think that they had been good friends long before last year's flight.
The meal marked one of the few times that they're both in the state at the same time; their jobs keep them traveling constantly. Addington, 44, is a management consultant. McKelvey, 33, works for an Internet infrastructure company.
Conversations between the new friends are filled with laughter and reflection. They offer colorful accounts of their travels and relive the ordeal of the April 7, 2005, flight - with each filling details the other may have forgotten.
"We met for the first time in a bar in Ellicott City on St. Patrick's Day [this year]," said McKelvey, "and it was like seeing an old friend. We have a lot in common, so we lean on each other a bit."
When McKelvey heard about the Vita (Latin for "life") award, she decided to find Addington and nominate him. United Airlines was able to put her in touch with not only her rescuer but Capt. John Heroux, who decided to land the plane based in part on Addington's concerns.
"You're in a million situations every day, but you will never be more vulnerable in your entire life than at 35,000 feet, and ... everything is out of your hands," said McKelvey. "You're totally at the mercy of people around you, and I feel very fortunate."
Addington is unassuming, and prefers not to draw attention to himself. But the former EMT doesn't hesitate when someone is in need. He said McKelvey is the fourth person he has helped in flight - though she was by far the most seriously ill.
McKelvey experienced severe back pain during the flight, but because she rarely gets sick she thought she had merely fallen asleep in a bad position. Yet with each breath, she felt a stabbing throb in her back.
A flight attendant placed an oxygen mask over her, and Addington began repeatedly checking her vital signs. It was about 3 a.m., and the flight was over the Midwest.
Addington asked the flight attendant to reach a doctor on the Airfone, knowing that hospitals across the country accept calls from airplanes. He told a doctor on the ground that he thought McKelvey had a punctured lung.
McKelvey, meanwhile, became terrified. "He's talking to the doctor, and what he's saying is scary. He's using medical language that I'd never heard. And I'm trying to communicate that it's not that serious because nothing's ever wrong with me."
Heroux had been told about McKelvey's condition and Addington's concerns and began preparing for a possible diversion - perhaps to Kansas City, Mo., although United's operations there were closed for the night.
Another option was to wait until the flight reached St. Louis; it has a much larger airport, and the distance would allow for an easier descent.
But McKelvey's condition was deteriorating, and Heroux, a 24-year pilot, said he decided on the steeper landing into Kansas City, pulling the plane "right up to the jetway so the EMT people could reach her immediately."
It wasn't until McKelvey was diagnosed at a Kansas City hospital that she was told how close to death she was. Blood clots that started in her legs had traveled up to the back wall of her lungs. (Healthy people do sometimes develop blood clots in their legs on long airplane flights. Doctors have long warned fliers to get up and move around on such flights.)
McKelvey said the doctor told her she needed to "find that man from the plane and thank him and that pilot," because it was unlikely she would have made it if they waited to land in St. Louis.
"You barely had minutes left," she recalled him saying, "much less hours."
McKelvey remained in the hospital in Kansas City for five days and recently completed blood-thinning treatment. While hospitalized, she wondered about the Samaritan who saved her - whom she knew only by his first name.
McKelvey received his e-mail address from United in March and immediately sent him a message.
"I still have it," Addington said. "In the subject line was, 'How to say thank you.' I read it, and I thought, 'Oh, my God.' At the time, I still didn't know how bad she was.
"She said, 'You changed my life. I wanted to thank you, and my family wants to thank you.' So we ended up meeting three days later."
Then, on April 8, McKelvey invited Addington's family over to her house to celebrate the anniversary of the lifesaving experience.
The two have found much in common: a devotion to family (she's a single mom of one, he's a married father of two) and to work that often has them flying twice a week to destinations around the world. They've gotten to know each other's families, and McKelvey's refers to him as her angel.
At their recent restaurant meeting, McKelvey said she used to be the kind of person who became flustered at the slightest inconvenience. Since her near-death experience, she's more in tune to her "to-do list."
"I had always wanted to take a solo vacation," said McKelvey. "I went to the United Kingdom [recently] with no itinerary, no place to stay, for five days. And I've gotten my [8-year-old] daughter exposed to travel; I sent her to golf camp in San Francisco. I'm big on exposing her to as much as I can."
Addington said that some EMTs won't get involved in in-flight emergencies for fear of litigation. He says they should help.
"I'm glad to have been a part of it," he said.
"I am, too," McKelvey added. "I'm really glad."