Asher said he followed all health and safety requirements and even asked the flight crew for permission before inking his seatmate.
"We followed all sanitisation protocols including prep, clean-up and disposal. We even asked the flight attendants, who gave us the go-ahead!"
Asher told BuzzFeed it all started when the woman complimented his tattoos, including Japanese designs, adding that she was looking to get a fairly simple tattoo on her trip.
"She seemed a little bit stressed about being able to find a shop and getting in, so at first, I jokingly brought up that I had all of my tattoo equipment with me," Asher told the publication.
"At first, it was just a casual suggestion, but as we continued talking, it seemed like she was very eager and comfortable with that experience, and she seemed to be looking for adventure on the trip."
There were hesitations from both parties at first but Asher said the spontaneous nature of the tattoo was actually part of the appeal.
"I did tell her that [the tattoo outline] was not gonna be stencilled, but she was very open to the idea of the tattoo having character. We even talked about bumps and turbulence," Asher told BuzzFeed.
His clip has since been viewed more than four million times with many applauding him over the mid-flight act.
"This is the coolest tattoo backstory," one TikTok user wrote.
"Would 100 per cent do this for the experience," wrote another.
However, not everyone was impressed, with some questioning how clean it would really be in a plane.
The US Transport Security Administration (TSA) shared the footage on their Instagram page, where people seemed more concerned than inspired.
One said: "This is so unsanitary and unsafe for literally everyone. Please don't encourage this kind of behaviour."
Another wrote: "I can't get a bottle of opened water on the plane and you got a whole tattoo gun."
Asher responded to some of the backlash saying he understood where people were coming from, but the decision to get tattooed ultimately rests with the client.
"At the end of the day, I understand it's not the most sanitary place to be doing tattoos – but we chatted about consent, risks, understanding and trusting each other first," he said.
The TSA also explained that tattoo equipment was indeed permitted in carry-on luggage.
Meanwhile, Asher told BuzzFeed his seatmate was thrilled with the final tattoo, and the two have now become friends and keep in touch.