Doubly vaccinated passengers will no longer have to take pre-departure Covid tests in England from 04:00 GMT on Friday, the government has said.
They will also not be required to self-isolate while awaiting test results after arriving in England.
If they arrive after 04:00 GMT on Sunday, people without symptoms will not need a PCR test if a lateral flow test is positive on day two.
The test changes come after travel firms called for them to be removed.
After the emergence of the Omicron variant, the government said all travellers over the age of 12 must show proof of a negative test lateral flow or PCR test taken within two days of setting off for the UK.
Fully vaccinated people are also currently required to pay for a PCR test within 48 hours of arrival, while those who aren’t must take pre-booked PCR tests on both day two and day eight after arriving, and self-isolate for 10 days.
Travellers currently must pay for private tests rather than using free NHS tests.
The prime minister said the pre-departure test “discourages many from travelling for fear of being trapped overseas and incurring significant extra expense”.
The announcement comes after airlines said passenger testing was making no real impact, with data last week suggesting one in 25 people in England had the virus.
They also said compulsory testing had held back the sector’s recovery.
Mr Johnson met his cabinet earlier and alongside changes to travel tests, the government has said it will ease Covid testing rules for people without symptoms, who will no longer need to confirm a positive lateral flow test with a PCR.
That rule change will come into force on 11 January and apply to England only for now.
On Tuesday, Boris Johnson said he hoped the country could “ride out” the current wave, although he acknowledged parts of the NHS would feel temporarily overwhelmed.
What are the current travel rules?
Currently, all travellers to the UK aged 12 and over have to show proof of a negative test, which can be a PCR or a lateral flow test, and must be taken up to two days before departure for the UK.
They then have to take another test – which this time must be a PCR test – within the first two days after their arrival in the UK.
But at the time that rule was brought in a month ago, the number of new cases reported in the UK each day was running between 40,000 and 50,000 – and was only rising relatively slowly because it was almost entirely made up of the Delta variant of Covid.
But UK cases have now risen sharply and Omicron is the dominant variant – so airlines can argue that there is no longer any hope of relying on testing to “keep out Omicron”.
EasyJet chief executive Johan Lundgren also welcomed the news, saying it would make travel “much simpler and easier”, as customers could now book and travel with “confidence”.
Shai Weiss, chief executive of Virgin Atlantic, added that the announcement meant customer demand would be boosted in a “critical booking window” for the industry.
The trade body Airlines UK has argued that continuing the current measures would be financially disastrous for the industry. Travel and tourism businesses have added that the current limits have depressed demand and dented consumer confidence.
Ahead of the test changes, Manchester Airports Group (MAG) sent the government research it commissioned, which it claimed shows that pre-departure testing has had little or no impact on the spread of Omicron.
It said that passenger numbers at MAG’s airports fell by more than 30% after Omicron measures were introduced.
Tim Hawkins, chief of staff at MAG, told the BBC’s Today programme the research showed there was a “basis for taking out all tests” related to international travel, due to the high number of Covid cases in the UK.
“We are beyond the point where international travel restrictions can play a role in managing that peak and if there is no benefit to it then we shouldn’t be doing it and we should take those measures out,” he added.
Separately, European airline and tour operator stocks rose on Tuesday amid a rise in investor confidence in the sector.
Hargreaves Lansdown analyst Susannah Streeter told Reuters: “With so many people in the short-term being forced to isolate at home, it’s likely many people will be spending the next few weeks browsing travel blogs for inspiration, given there is so much desperation for a holiday.”
A recent report by aviation analytics firm Cirium found that the Covid pandemic triggered a 71% drop in international flights in and out of the UK in 2021.