Airlines were hit with more than 600 fines for flying passengers to the UK without the correct paperwork.
Britain's Department for Transport said 630 infringements had been issued since February 11 – when the UK increased border measures to prevent imported coronavirus cases.
Airlines face fines of up to £2,000 ($2,777) for each passenger who is allowed on board without recent proof of a negative Covid-19 test or a completed passenger locator form.
Airlines can be fined a further £4,000 for failing to properly inform passengers of the UK’s border requirements, while they face a £2,000 fine for bringing red-list travellers to a non-designated port.
Passengers face a £500 fine if they do not have the right documents.
The transport department said the fines form part of the country’s "tough border measures to protect the UK as the vaccine rollout continues to make progress”.
It said Border Force officers were “currently checking every individual coming into the country, no matter where they have come from, and will continue to carry out thorough checks at the border to keep the public safe”.
The fines are issued by the Civil Aviation Authority.
The UK's new customs checks led to queues of up to six hours at the border because of a shortage of border staff.
This month, Heathrow Airport's chief solutions officer Chris Garton demanded that the government introduce quicker checks to help deal with the delays.
“We need to see a dramatic improvement in border performance if we are to increase passenger numbers travelling through Heathrow,” he told a parliamentary transport committee. "The situation is becoming untenable."
