Hundreds of Britons caught up in the ash flight ban remain stranded at Bangkok's airport as anti-government protests take place in the capital.
Tourist Emma Stubbs said Suvarnabhumi Airport was "like a concentration camp" with travellers staying overnight as riots flared in the city.
The Foreign Office advised against non-essential travel to Bangkok but said the unrest did not affect the airport.
Others left stranded elsewhere are returning to the UK in cruise liners.
Ash from the Icelandic volcano has caused further disruption to airports in the Highlands and Islands, with Inverness, Wick, Kirkwall and Stornoway airports all closed until at least noon because of a high density cloud of ash overhead.
A spokeswoman for the Civil Aviation Authority said all other UK flight paths were now clear.
The Department for Transport said restrictions on night flights to and from Heathrow, Gatwick and Standsted had been relaxed on Wednesday and Thursday night to clear the backlog.
The European air traffic agency Eurocontrol said European air traffic had returned to normal, with 29,000 flights expected on Friday, the Reuters news agency reported.
The Association of British Travel Agents said that almost all stranded British tourists had returned, with some 51,000 coming back on Thursday after UK flight restrictions as a result of a volcanic ash cloud from Iceland were lifted.
On Thursday night, 75 people were being treated in hospital after clashes between anti-government protesters and riot police in the Silom business district of Bangkok.
Early on Friday, hundreds of riot police crossed a major road to confront red-shirt anti-government protesters.
But the police later stepped back from confrontation and the reds agreed to move further away from their barricade.
Reports had said that three people were killed, but the government later said that one person died.
With unrest flaring in the city, Ms Stubbs told the BBC that the mood in the airport was "dog eat dog" as travellers camped out to secure a flight back home.
She said: "It's like a concentration camp. And although there is camaraderie - there is also competition.
"We have heard of other passengers who have lied - making up sob stories - so they get prioritised over the rest of us who are stranded".
Tim Rutledge of Portsmouth, Hants, who has been stranded since Sunday, told he felt the government was not doing enough to help.
He added: "The situation is getting worse and worse. Am I worried for my safety? Yes I am - because our government is not doing anything to help get us out of here".
The Foreign Office said Britons "should exercise extreme caution throughout the country".
However, Quinton Quayle, the UK ambassador to Thailand, told BBC Radio 5 Live that there was was "no security issue" at the airport.
He added: "We've had a team all day of about seven embassy officials giving advice on flights out of Bangkok because clearly people have been severely disrupted.
"We're giving every help we can to get people on flights as soon as possible".
'Significant repatriation'
Thomson said two of its cruise ships had been involved in a "significant repatriation programme" in response to six days of UK flight cancellations.
Some 2,200 travellers are on board the new £500m Celebrity Eclipse, en route from Bilbao, Spain, to Southampton.
The Thomson cruise ship Island Escape is sailing back from Madeira with 1,600 passengers and will arrive in Cornwall.
Island Escape was due to dock in Falmouth, Cornwall, on Friday morning.
Celebrations to mark the inauguration of the luxury Celebrity Eclipse had to be put on hold to pick up customers of tour operators Thomas Cook, TUI and Co-Op Travel Group.
Dan Hanrahan, chief executive of Celebrity Cruises, said: "There have been some incredible logistics involved in the last 24 hours".
The Celebrity Eclipse is expected to arrive between 1700 and 1900 BST.
Meanwhile, RAF Typhoon jets are flying again after being grounded by fears over volcanic ash.
A spokesperson for the MOD told BBC Lincolnshire that all 11 aircraft have been checked and no problems have been reported.
Flights were suspended on Thursday when ash deposits were found in the engines of four aircraft.
Night trains
Railway lines serving Heathrow, Gatwick and Stansted airports from Paddington, Victoria and Liverpool Street stations in London operated through the night into Friday morning.
There were also extra services running into the early hours to the main ferry ports, including Dover, Kent.
Engineering work on the East and West Coast Main Lines between London and Scotland was cancelled to enable more direct services to run.
The eruption of the Eyjafjallajokull volcano in Iceland from 14 April sent vast amounts of ash into the atmosphere.
There were fears the ash could pose a risk to jet engines but flight restrictions were lifted on Tuesday night after regulators tested the impact on aircraft.
The cost to European tourism has been 1.72bn euros (£1.49bn), according to a World Tourism Organisation estimate reported by the AFP news agency.
BBC News
