People in the UK are not allowed to fly into Turkey due to the COVID-19 situation in the country. With 6,000 fans from both City and Chelsea allowed in the stadium, the UK government's decision to place Turkey on its "red list" would have prohibited fans from attending the showpiece final, which led to UEFA looking for alternative options.
"I think we can all agree that we hope never to experience a year like the one we have just endured," UEFA president Aleksander Ceferin said. "Fans have had to suffer more than 12 months without the ability to see their teams live and reaching a Champions League final is the pinnacle of club football.
"To deprive those supporters of the chance to see the match in person was not an option and I am delighted that this compromise has been found. After the year that fans have endured, it is not right that they don't have the chance to watch their teams in the biggest game of the season."
Later on Thursday, the Portuguese government said English fans attending the Champions League final in Porto will have to fly in on the day of the match and will need to stay in a "bubble" before flying back straight after the game, the Portuguese government said on Thursday.
Portugal's Cabinet Affairs Minister Mariana Vieira da Silva told a news conference that a set of rules had been put in place for those fans attending the final.
"Those who come to the final of the Champions League will come and return on the same day, with a test done, in a bubble situation, on charter flights.
"There will be two fan zones and from there they will be moved to the stadium and from the stadium to the airport, being in Portugal less than 24 hours."
Vieira da Silva said that the local health authority was in charge of selecting seats for fans to ensure social distancing and that tickets were non-transferable.
Sources told ESPN on Saturday that UEFA were in talks with UK government about moving the final to England. However the UK government would not grant quarantine exemption to approximately 2,000 UEFA staff, broadcasters, sponsorship partners. Failure to find an agreement meant European football's governing body had to look elsewhere.
"We accept that the decision of the British Government to place Turkey on the red list for travel was taken in good faith and in the best interests of protecting its citizens from the spread of the virus but it also presented us with a major challenge in staging a final featuring two English teams," Ceferin said.
"The difficulties of moving the final are great and the FA and the authorities made every effort to try to stage the match in England. I would like to thank them for their work in trying to make it happen."
The Portuguese FA (FPF) had offered to host the event and following the UK government's decision to place Portugal on the "green list" -- meaning those travelling do not have to quarantine on return. With travel restrictions lifted for City's and Chelsea's supporters, UEFA opted to move the final to FC Porto's Estadio do Dragao.
"Once again we have turned to our friends in Portugal to help both UEFA and the Champions League and I am, as always, very grateful to the FPF and the Portuguese Government for agreeing to stage the match at such short notice," Ceferin added.
"They have worked tirelessly in very tight time constraints in finding solutions for the many challenges that hosting a game of this magnitude presents. Whenever there has been an obstacle, they have been creative in the solutions presented and the success of staging this year's final is entirely down to their hard work and persistence."
It means for the second season running, the Champions League final will be moved from Istanbul to Portugal, with the 2020 showpiece between Bayern and Paris Saint-Germain staged at Benfica's Estadio da Luz stadium in Lisbon. Bayern won the game 1-0.
This season sees City in their first final, while Chelsea are aiming to win the competition for the second time, having last won it in 2012.
"I hope to be in Istanbul and Turkey for a Champions League final and many other events in the near future," Ceferin said. "I hope the final will be a symbol of hope at the re-emergence of Europe from a difficult period and that the fans who travel to the game will once again be able to lend their voices to showcase this final as the best in club football."