On the video Elin Ersson streamed live on Facebook on Monday, you can hear irate plane passengers shouting: “We want to go, sit down!” Ersson, her cheeks reddening slightly and her eyes becoming teary, remains standing, and her voice is steady. A member of the cabin crew on the flight from Gothenburg to Istanbul repeatedly asks her to turn off her phone and sit down, or leave the plane. He describes her as an “unruly passenger”. Ersson, young and slight, stands her ground. “I’m doing what I can to save a person’s life,” she says.

Did she feel awkward, or exposed? “I was so caught in the moment that I didn’t really realise that everyone was looking at me,” says Ersson on the phone from Sweden. “My focus was all on stopping a deportation to Afghanistan.”

More than two million people have now watched the video of Ersson’s protest as she attempted to stop the deportation of an asylum seeker. “I’m not going to sit down until this person is off the plane,” she says, and she remains standing, her phone’s camera focused on her face because other passengers didn’t want to be filmed. The atmosphere seems hostile. An unseen British man approaches her. “You’re upsetting all the people down there,” he says. “I don’t care what you think.” He tries to take her phone, but a flight attendant gives it back. Someone else says: “You’re preventing all these passengers going to their destination.” Ersson has an untouchable comeback: “But they’re not going to die, he’s going to die.”

She finally breaks down on the film, not from the hostility of a handful of people, but from the uplifting support of other passengers. People start applauding her; a man three rows away stands up to tell her he is with her. A football team at the back of the plane stand up, too.

Play Video 3:22 'Not sitting down': student Elin Ersson halts deportation of asylum seeker – video

“It felt good, when the Turkish guy started talking to me and making sure that I knew I wasn’t alone,” says Ersson. “It felt really good. He was saying what I was doing was right.” The person whose deportation Ersson thought she would be stopping was a young Afghan man, although once she was on the plane, she realised he hadn’t been put on it. However, his family and Ersson had been approaching people at the airport before the flight to inform them what was happening. Among the people they had spoken to was the football team who “were supporting the cause, so I knew that I had people supporting the idea of me standing up. I had the mental support that I needed.”

Instead, an Afghan man in his 50s was being deported. Finally, he was taken off the plane through the rear exit, although Ersson didn’t witness this – other people were standing up to watch – and she didn’t see him on the tarmac either, once she left the plane. “They made me go out of the front of the plane and I couldn’t see with my own eyes, but they are saying he was there, and I heard them speaking with each other and it really sounded like his deportation was cancelled.” She adds: “It felt good.”

Ersson, 21, a student at the University of Gothenburg training to become a social worker, has been volunteering with refugee groups for about a year. In 2015, 163,000 people sought refuge in Sweden, including 35,000 unaccompanied minors, but the government has been pursuing a deportation policy, especially of Afghans. Afghans make up more than half of refugees, but only 28% have been granted asylum. Afghanistan is considered “safe”, although humanitarian groups point out it is a fragile country in the grip of conflict – more than 3,000 civilians were killed and 7,000 wounded in 2017.

“People there are not sure of any safety,” says Ersson. “They don’t know if they’re going to live another day. As I’ve been working and meeting people from Afghanistan and heard their stories, I’ve been more and more in the belief that no one should be deported to Afghanistan because it’s not a safe place. The way that we are treating refugees right now, I think that we can do better, especially in a rich country like Sweden.”

This September, Sweden will hold a general election, and immigration has already dominated the debate. Polls have shown strong support for the anti-immigration party Sweden Democrats, which has links to white supremacists and neo-Nazi groups. Ersson is concerned the country is shifting to the populist far right. “I’m meeting Nazis on the street every month or so. I sense they’re getting strength and people are going to be able to vote for the [Sweden Democrats] when we have the election.”

She has been gratified by the global response to the video. “I hope that people start questioning how their country treats refugees. We need to start seeing the people whose lives our immigration [policies] are destroying.”

Ersson has been involved in trying to stop deportations before – helping refugees access legal help and stalling the removal process – but this was the first time she had made it on to a plane to intervene. A group of activists, mainly connected through Facebook, had heard that a young man was about to be deported. People chipped in with money for a plane ticket; Ersson went home to get her passport and headed straight to the airport.

It turned out he wasn’t on the plane, but “there were rumours going around” that immigration officials had been moving other people due to be deported. They figured out an Afghan man in his 50s was among them. Ersson didn’t know anything about him, even what he looked like, but she soon realised he was on the plane and the young man wasn’t. Ersson approached him at the back and spoke to him briefly before one of the security guards accompanying him pushed her away.

“When she started to touch me and push me I took up my phone and started filming in case something happened to me, and I wanted to make sure that other people knew what was going on,” says Ersson, who shot the video from near the front of the plane where her seat was. The live stream also meant the family of the young man, who were still at the airport, would know that he hadn’t been put on that plane.

Ersson was aware that many of the passengers were frustrated. “First they got annoyed because the flight attendants were talking to me and I wasn’t listening, but when they [realised] what I was doing then most of them thought it was good.” She was determined, she says. “The British guy was really aggressive but I knew that I had legal rights on my side … I knew I would have back-up from security on the plane. Even though he was frustrated because his plane was late, I knew he wasn’t allowed to touch me or take my phone.”

By the end, she says: “Most of all, I felt supported by the people on the plane. It was really emotional but I had a mission and I was just making sure I was fulfilling that.” She said she was nervous at the airport and not sure if she would succeed. “It felt like that when I saw the family crying and I didn’t know if I was going to be able to do it,” she says. “But I knew that I couldn’t back down because it was my name that was on the ticket. I had to do what I could.”

The tragic postscript is that she believes the young man she was originally trying to stop getting deported was taken to Stockholm and put on a flight there. “This is how deportations in Sweden work. The people involved know nothing and they are not allowed to reach out to their lawyers or family,” she says in a text the next day. “My ultimate goal is to end deportations to Afghanistan.”