Prime Minister Gordon Brown has warned holidaymakers to expect a summer of delays at airports - following three failed car bombings in Britain.
He told BBC One's Breakfast programme it would be "very difficult for people" but said the public wanted to know they would be safe in crowded places.
He also praised bomb experts in London, Glasgow airport workers who tackled the bombers and the police investigation.
"I think we have seen in the last week the best of Britain," he added.
Last Friday two Mercedes containing petrol, gas cylinders and nails were found in central London and on Saturday a burning Jeep Cherokee loaded with gas cylinders crashed into the doors of Glasgow Airport.
The cars in London failed to explode, while the two suspects in Glasgow were tackled by police and bystanders after the jeep crashed.
Mr Brown said the fact that there had been no loss of life was a tribute to the vigilance of the British public and the emergency services.
"I think we saw in the last week the best of Britain, people coming together in the face of a terrorist threat and Britain showing to the rest of the world that we would be unyielding any time that anybody tries to do damage to our country."
And he praised the speed of the investigation - which has included raids in Australia, saying he believed they were "getting to the bottom" of the attacks.
He said he wanted to reassure the public that the authorities had acted very quickly to deal with potential future incidents.
He said a review of NHS recruitment - instigated after it emerged that eight of the suspects had links to the health service - would report on Monday.
'Hearts and minds'
But he added: "Crowded places and airports, I think people will have to accept that the security has got to be more intense.
"We have got to avoid the possibility, and it's very difficult, that people can use these crowded places for explosions."
Mr Brown said that he thought people would understand, and would want to know that they would be safe.
A jeep was driven into the front of Glasgow airport on Saturday
The prime minister also said he wanted to see an international register of potential terrorists, more work with foreign authorities and better co-ordination internationally - and between the armed, security and emergency services, as well as the strategy to win "hearts and minds".
He also pledged to take on the al-Qaeda' propaganda battle culturally and in the media, to isolate the extremists.
"What we have got to do however is to persuade people that the values we hold important are the values of all decent people in all religions and all faiths," he said.
And he denied that the government's response to the widescale flooding in the north of England had been delayed by the handover of power from Tony Blair, following criticism that Hull - where 10,500 homes have been evacuated - had been "forgotten".
He said: "Where there is an emergency, where there's a crisis, we have acted immediately and we will continue to do so."