A further 800 troops have been sent to Dover to help thousands of lorry drivers stuck at the French border.
Some 1,100 troops have been deployed as part of the operation at the English Channel border after France closed its border last Sunday.
The travel ban, which was lifted on Wednesday, followed the discovery of a fast-spreading new strain of Covid-19 in the UK and caused severe disruption at the Port of Dover.
The army personnel will be carrying out mass testing and distributing food and water, according to the Ministry of Defence.
About 5,000 lorries are still at Manston Airport waiting to cross the Channel, with many of the drivers now forced to spend Christmas Day and Boxing Day in their lorries.
On Thursday, one haulier who was not able to make it back home to Bulgaria in time for Christmas Day told HuffPost UK: “I said if I broke down I’d fly back, that I’d do whatever it takes,” he said.
“But, she’s accepted it. This is beyond my control.”
“The last promise I made before I left was: ‘I’ll be back for Christmas’. I didn’t say which one.”
Drivers are now allowed to cross into France if they can show proof of a negative coronavirus test result taken within the past 72 hours.
On Friday, transport secretary Grant Shapps said more than 10,000 tests had been carried out, 24 of which had come back positive for Covid-19.
He said: “We need to get the situation in Kent, caused by the French government’s sudden imposition of Covid restrictions, resolved as soon as possible.
“I know it’s been hard for many drivers cooped up in their cabs at this precious time of year, but I assure them that we are doing our utmost to get them home.”
Traffic was moving smoothly through Dover on Friday morning, with French firefighters and a group of Polish medics also supporting the testing effort.
Germany’s ambassador to the UK, Andreas Michaelis, said some German hauliers had managed to make it home for Christmas, while others remained in Kent.
He tweeted: “Some of the German lorry drivers we’ve been in touch with are on their way home or at home already. Others sadly remain stuck.
“I sincerely hope things will start moving for them soon. This is a difficult Christmas. Our thoughts are with them.”
In a tweet, the MoD said: “We are deploying a further 800 personnel to Kent today to support an increase in the testing capabilities to help clear the backlog of vehicles and ensure traffic can begin to move at a closer to normal pace through Dover.”
A Port of Dover spokesperson said ferry services ran throughout Christmas Eve night and will continue on Christmas Day to help ease congestion.