LONDON - British pilots, cabin crew, travel agents and other workers are urging politicians to save the summer holiday season by reopening routes abroad or risk destroying tens of thousands of jobs as companies fail.

Workers from the travel industry will demonstrate across Britain on Wednesday, protesting outside parliament, meeting politicians, and holding events at airports to highlight the threat to their jobs from the government's strict rules.

England is expected to re-open from a third COVID-19 lockdown in July but the travel sector remains effectively shut, with the government advising against travel except to a handful of destinations.

British government ministers are examining ways to re-open travel more broadly, and are considering plans to ditch quarantine requirements for vaccinated adults and their children to some destinations. 

But Prime Minister Boris Johnson has said that whatever happens, it will be a difficult year for travel.

The industry says the rules need to be eased as soon as possible or tens of thousands more jobs will be lost as companies fail.

"The government has to decide if this summer it will make or break the UK travel industry," said? Brian Strutton, acting General Secretary of the British Airline Pilots Association (BALPA).

To survive more than 15 months of travel restrictions, companies including British Airways, easyJet, TUI and Jet2, have taken on billions of pounds of debt.

"Airlines are at the absolute limit of what they can borrow and without a genuine reopening this summer they will require government support to survive," the chief executive of industry group Airlines UK Tim Alderslade said.

Under the government's traffic light system, only travellers to a small number of green-list countries can avoid quarantine.

Popular European holiday destinations for Britons, including France, Greece, Italy, Portugal, Spain and the United States, are rated amber and require returning passengers to take three expensive COVID-19 tests and isolate for 10 days on return.

The industry urged the government to expand the green list when the system is reviewed on June 28.

EasyJet's head of cabin crew Tina Milton said her staff were joining events on Wednesday "to speak up for travel and show support for the industry we all work for and love".

Airline bosses have said that they could be ready for a wider re-opening of travel within weeks should government rules change.

But even if Britain eases its rules, airlines and tour operators could still face a challenge as the spread of the Delta variant of COVID-19 has prompted other countries to place restrictions on British arrivals. 

(Reporting by Alistair Smout and Sarah Young; editing by Guy Faulconbridge and Barbara Lewis) ((alistair.smout@thomsonreuters.com; +44 207 542 7064; Reuters Messaging: alistair.smout.thomsonreuters.com@reuters.net))