A ticket mix-up left a man in the airport terminal in Tehran while his wife boarded the flight that crashed soon after take-off on Wednesday, killing everyone on board.
Mohsen Ahmadipour was supposed to have taken the Ukraine International Airlines flight, but his ticket had been accidentally cancelled, meaning his life was spared while his wife died.
The 38-year-old was still inside the terminal when he learned the Kiev-bound flight had crashed to the ground in flames just minutes after take-off and none of the 176 people on-board had survived. His wife of almost six years was among them.
Mr Ahmadipour's story is one of hundreds of heartbreaking tales emerging from relatives of those killed.
The couple, who lived in Ottawa, Canada had been visiting family in Iran, according to news site 'Ottawa Citizen'.
Roja Azadian (43) boarded the flight, having arranged that her husband would join her when he could get another plane. It would be the last time the couple saw each other.
For another couple, the flight would be the start and end of a marriage.
Pouneh Gorji (25) and Arash Pourzarabi (26) were travelling back from their wedding in Iran, along with four other members of their wedding party.
"If you met them, even once, you could tell that these two belonged together for sure," Amir Forouzandeh, a friend of the couple, told a local news website.
The University of Alberta graduates boarded the flight together just days after their wedding, preparing a local celebration for friends in Canada who couldn't make the wedding in Iran.
"I don't have enough tears to cry for them," their friend Orod Kaveh posted on Facebook.
Saeed Tahmasebi, a British national and also a newly-wed, died in the crash along with his wife Niloufar Ebrahim.
The couple were only on the flight because they had waited behind in Iran to pick up their wedding photographs.
Dozens of couples, families and children were aboard the flight, which was in the air for no longer than 10 minutes.
Condolences flooded social media as Ukraine International Airlines released the roster of names of people on the flight. "One of my wonderful PhD students, Ghanimat Azhdari, was on the plane that crashed in Tehran this morning," Dr Faisal Moola of the University of Guelph tweeted.
Ms Azhdari was a PhD student in the department of geography, environment and geomatics.
Her PhD research was devoted to advancing the rights of indigenous peoples in conservation and the protection of biocultural knowledge.
"The students and I are in so much pain," the tweet read.
Many of the passengers on the flight are thought to have been heading towards Canada via Kiev.
One of them, Forough Khadem (38), a "promising scientist", was returning to Winnipeg after visiting family in Iran. She graduated with a PhD in immunology from the University of Manitoba.
Her research had given rise to a new understanding of the deadly parasitic disease, leishmaniasis.
"Forough was one of my best PhD trainees, an outstanding scientist and above all an amazing human being," Jude Uzonna, an associate professor at the university, told Canadian channel CBC. "I am utterly devastated and trying to grapple with this."
Dr Khadem, the daughter of a university professor, grew up between Iran and New Zealand before moving to Canada.
"She radiates love. She radiates humanity. She radiates empathy. Once you see her, you want to know who she is," Ms Uzonna said.