A questionmark has been raised over a potential travel corridor between New York and London by the boss of Delta Air Lines.
Chief executive Ed Bastian insisted it would be easier to relaunch transatlantic flights to “just about any” other European capital.
Airlines struggle to establish routes not exempted from stringent Covid-19 quarantines.
He told the Financial Times: “I think New York-London is complicated… I think you will find on the continent several countries that are more open.”
His comments follow transatlantic partners British Airways and American Airlines joining United Airlines in introducing Covid-19 testing on selected fights from the US to London.
A task force comprising Oneworld member airline representatives and independent medical experts will monitor the BA-AA trial and share results with the US and UK governments.
The objective is to “demonstrate the essential role that Covid-19 testing programmes can play in safely restarting travel”.
The UK is expected to announce plans to cut quarantine times for incoming passengers from 14 days to around a week, but even that may not be enough to help revive the route.
The main avenue of recovery may be through business travel, despite more pessimistic views from Microsoft co-founder Bill Gates, who predicted that more than half of business trips will “go away” due to the rise in video conferencing.
But Bastian said: “I think business travel’s going to be strong on the way back. Bill Gates is not a road warrior … he’s not the person to be forecasting that.”