Restrictions on entering the US have been loosened.
Fully vaccinated travellers - from more than 30 countries including the UK - can visit for the first time since the start of the pandemic.
What are the new US rules?
Vaccinated people who have had a negative test taken no more than three days before travelling can enter without quarantining.
Another test three to five days after arriving in the US is recommended.
Vaccine certificates including the NHS Covid Pass are accepted.
Children under 18 do not need to be vaccinated, but should also take a test after arriving.
Masks are mandatory on planes and in airports and travellers must follow state and local rules at their destination.
Is there still a red list?
The last of the nations on the UK's red list have been removed.
Under red-list rules, travellers were only allowed to enter the country if they were a UK or Irish national, or a UK resident. They had to quarantine for 10 days, at their own expense, in a government-approved hotel.
Transport Secretary Grant Shapps said countries could be added to the red list again if needed.
In a separate change, travellers to Scotland, Wales and Northern Ireland can now take a lateral flow test two days after arriving - instead of a more expensive PCR test. This follows a similar move by England last month.
What are the new rules for travelling to the UK?
Before travelling
Fully vaccinated passengers travelling to the UK no longer have to take a Covid test before setting off.
This applies to people vaccinated in the UK, the EU, the US and dozens of other recognised countries - including Brazil, Hong Kong, India, Pakistan, South Africa and Turkey.
You must be able to prove you are fully vaccinated before travelling.
The changes also apply to under-18s resident in one of these countries, whether or not they are vaccinated.
Upon arrival
Fully vaccinated people coming to the UK need to take a lateral flow test two days after arrival.
Passengers need to book tests before travelling to the UK. They must send a picture to verify the result. The lateral flow tests for travel must be bought from private providers - NHS kits cannot be used.
Passenger locator forms remain compulsory.
What if I'm unvaccinated?
If you aren't fully vaccinated - and you're over 18 - you must self-isolate at home for 10 days after arrival in the UK.
You also need to
take a PCR or lateral flow/antigen test (not a free NHS test) in the three days before you travel to the UK
take a test on or before day two and on or after day eight after your return.
Test to Release will remain an option for unvaccinated passengers to England who want to shorten their quarantine.
What else do I need to do before I travel?
You need to keep checking the rules for your destination country as these can change at short notice.
The UK Foreign Office provides country-by-country travel advice.