Many holidaymakers in England are eagerly awaiting changes to the government's travel green list, in the hope that more destinations will be added.
However, there are concerns that rising coronavirus cases including the delta variant (formerly known as the Indian variant) could impact on summer plans.
The government is said to be updating the traffic light destination system on Thursday, which could see countries moving between the green, amber and red lists.
There is growing speculation that popular holiday islands could be added, including Spanish and Greek islands plus Malta.
What are the rules for people returning from each category?
Green: There is no need to self-isolate. Take a pre-departure test and a PCR test on day two of your arrival in the UK.
Amber: Self-isolate for 10 days, unless you receive a negative result from a test taken at least five days after arrival. Take a pre-departure test, and PCR tests on day two and day eight of your arrival in the UK.
Red: Spend 10 days in a quarantine hotel. Take a pre-departure test, and PCR tests on day two and day eight of your arrival in the UK.
On Wednesday, Boris Johnson warned the government will have “no hesitation” over moving countries off the green list if necessary, and said it will “wait and see” what the recommendations of the Joint Biosecurity Centre are before announcing changes to the travel lists.
People returning to the UK from green locations are not required to self-isolate, and only need to take one post-arrival coronavirus test.
Of all the countries on the current green list, Portugal has been the most popular and practical destination for Brits.
Although there have been reports that it could be downgraded in the future.
Travellers returning from amber list locations, which includes popular hotspots such as Spain, France, Italy and Greece must quarantine at home for 10 days and take two post-arrival tests, while there is a travel ban to red list countries.
Robert Boyle, former director of strategy at British Airways’ parent company IAG, predicted that a number of summer hotspots will be added to the green tier.
He wrote in a blog post: “It still seems very likely that whilst Spain and Greece will not make it onto the green list, many of their islands will, due to lower case rates and higher vaccinations than on the mainland.”
Mr Boyle added: “Malta, Finland and Slovakia are fairly safe bets, based on high testing rates and low reported cases.”
On Wednesday, the prime minister said "caution" was needed over putting holiday destinations onto the green list.
“We are going to try and allow people to travel as I know many people want to, but we’ve got to be cautious," Mr Johnson said.
“We’ve got to continue to put countries on the red list, on the amber list, when that is necessary.
“We will have no hesitation in moving countries from the green list to the amber list to the red list if we have to do so.
“The priority is to continue the vaccine rollout to protect the people of this country.”
Debate is continuing over whether the final stages of unlocking restrictions in England can go ahead on June 21, due to concerns over the spread of the coronavirus variant first identified in India.
The Daily Mail reported ministers also have been alerted to a variant first thought to have originated in Nepal, suggesting this could have an impact on holidays.
Ahead of any announcements, one industry expert said several Greek islands, Malta and parts of the Caribbean could be added to the green travel list on Thursday.
Paul Charles, chief executive of travel consultancy The PC Agency, said a number of popular holiday destinations “really deserve” to be moved to the low-risk tier.
Mr Charles said he expects additions to the list to include the Greek islands of Zante, Rhodes and Kos, the Caribbean islands of Grenada and Antigua, plus Malta and Finland.
The transition of those locations to green status would be “a boost” to the struggling travel industry, he said.
Assessments are based on a range of factors, including the proportion of a population that has been vaccinated, rates of infection, emerging new variants, and access to reliable scientific data and genomic sequencing.
Mr Charles said he would be “surprised” if Spain’s Balearic Islands – including Ibiza, Majorca and Menorca – are added in Thursday’s update.
“They’re hugely popular and I’m not sure the government is ready to encourage so much travel at the moment.”
On Wednesday, the CEO of Ryanair predicted that the Greek islands, Balearics and Canaries could be added to the green list.
Michael O'Leary, who has been critical of the government's travel policies throughout the pandemic, said restrictions being lifted for the islands would be a "good starting point". However, he added that the current traffic light system is "confusing".
Mr O'Leary also believes there's no basis for any limits on travel after June.
Which countries will be added to the list? Mr O'Leary gives his predictions.
The vaccination programme is seen as key in the bid to reopen the country and beyond.
It was confirmed on Wednesday that 75% of UK adults across the UK had now had their first coronavirus jab, and 50% of adults in England had received both doses.
The UK could hit another major milestone on Thursday, passing the point of half of all UK adults receiving both doses of a coronavirus vaccine.
Latest figures suggest 49.5% of the UK population aged 18 and over have had two jabs.
Government figures, based on people who died within 28 days of testing positive for Covid-19, said a further 12 people had died within 28 days of testing positive for Covid-19 as of Wednesday, bringing the UK total to 127,794.
The government also said that, as of 9am on Wednesday, there had been a further 4,330 lab-confirmed cases in the UK.
It comes after zero Covid-19 deaths were reported in the UK on Tuesday.
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