In 1933, 23 countries, including austria and australia, syria and south africa, signed the international sanitary convention for aerial navigation to deal with plague, cholera, yellow fever, typhus and smallpox. before departure from infected areas, planes were to be cleaned, crew and passengers inspected and anyone showing symptoms, as well as persons in close relations with the sick, excluded. any rats on board would be exterminated.

If during a flight a smallpox case was discovered, the sick passenger and those who might have been exposed to them were to be quarantined on arrival. there were exceptions for those with proof of a previous attack of smallpox or a vaccination within less than three years and more than 12 days.

If people are to fly between countries, passengers must feel safe. thats why, when flying took off after the second world war, governments established the international civil aviation organization to agree global rules. after the 9/11 attacks, the industry, through icao, brought in new security measures, such as reinforced lockable cockpit doors. and, in 1933, when commercial aviation was in its infancy, those 23 governments knew they needed to act jointly to still anxiety about diseases spreading.

What is happening today is in stark contrast. each government has its own rules. travellers to france from a range of countries, including other eu nations, the uk, new zealand and rwanda, can enter without restrictions. others need a specific reason for their trip, such as being health professionals fighting covid-19, and may, depending where they have come from, have to produce a negative covid-19 test result carried out less than 72 hours before departure.

You cant get into hong kong unless you are a resident. you cant travel to the us if you have been in the uk, ireland, the schengen area, iran, brazil or china in the previous 14 days. you will have to self-isolate for two weeks if you arrive in england from a host of countries, including france, but the rules may differ if you are going to scotland, wales or northern ireland.

Its no surprise that international passenger traffic worldwide was down 91.8 per cent in july on the previous year and 88.3 per cent down in august. of course, many people do not want to fly at the moment anyway and there are some, including a few readers of this column, who think it would be wonderful if no one ever flew again.

Its inevitable that countries will have their own entry requirements based on their assessments of where the disease is prevalent. but if flying is to resume, governments, regulators and the industry need to move towards a common system of assuring themselves, and passengers, that people flying are infection-free.

The industry recognises this. they are begging governments to act. londons heathrow is asking for government support for their on-site testing facility so that arriving passengers who test negative can escape quarantine. but whats really needed is action before passengers board.

The key to restoring the freedom of mobility across borders is systematic covid-19 testing of all travellers before departure, alexandre de juniac, director-general of the international air transport association, said last month.

This may look like a steep demand when even uk healthcare workers are struggling to get their families tested. but air passengers should pay for tests, just as they have to pay for yellow fever vaccinations for countries that still demand them. at least, governments should aim for a common standard that allows travellers to fly again. their equivalents in previous generations knew what was required.

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