Covid-19 tests on arriving passengers are “not the panacea” for relaxing travel restrictions, aviation sources involved in government talks say.

Heathrow confirmed a Covid test trial on passengers arriving at Terminal 2 this week with chief executive John Holland-Kaye declaring: “We’ve got to have a different fallback to complete quarantine.” He suggested “a testing system on arrival for passengers from ‘red’ countries” would provide an alternative to quarantine restrictions under the government’s Covid traffic-light system.

Following travel’s restart to destinations mainly in Europe on July 10, an airline source said: “Now travel corridors are up, we need to speak about testing [and] what might it take to get a market like the US going?”

However, an aviation source warned: “Testing is not the panacea everyone thought. We’re getting push backs from Public Health England on how effective testing can be at borders. It poured cold water over the idea of a test on arrival or departure.”

The source noted: “Testing is one of the only ways to free up quarantine to red countries. The alternative is just a continuation of quarantine. [But] testing once is not effective. There needs to be more work. The testing of NHS staff is regular so asymptomatic workers are captured and self-isolate.”

The Foreign Office removed Serbia from the list of countries open to travel on the day the quarantine-free list came into force, leading Tui UK chief executive Andrew Flintham to demand the government add destinations to the ‘safe’ list just as quickly. He also criticised the Scottish government for omitting Spain from its ‘safe’ list, a decision dubbed “very disappointing” by the Scottish Passenger Agents’ Association, which represents 120 travel agents north of the border.

Flintham said: “We get that the government may remove destinations. We ask that they are equivalently flexible when they add destinations.”

However, an airline source insisted: “We don’t expect any relaxation before the first review on July 27.” The source said removing quarantine restrictions from passengers transiting from a ‘green’ country to the UK via an airport in a ‘red’ country such as Dubai, was now a priority, saying: “We’re pushing for that to be examined at the first review.”