We must not return to pre-covid levels of international air travel if we are to hope to avert climate catastrophe and reduce the risks of future pandemics, argue these authors
Despite knowing that RNA viruses such as pathogenic avian influenza, Nipah, Ebola, HIV, and more recently SARS-CoV-1 and MERS, readily infect new hosts and have a high mutation rate, the UK and many other countries were unprepared for the SARS-CoV-2 pandemic. 
Aviation is now a major vector for the introduction and transmission of infection worldwide.  Following the global spread of SARS-CoV-2, variants of concern have been identified in the UK (Alpha), South Africa (Beta), Brazil (Gamma), and most recently India (Delta), which have in turn also spread rapidly across the globe.  The UK is both an importer and exporter of these variants. Border controls in the UK have been implemented too slowly and are too piecemeal to prevent or slow this global spread.  The year 2020 was declared by the aviation industry as the worst year in its history from a financial perspective, and the latest threat from the rapid spread of the Delta variant and the potential for more variants of concern, has again derailed international air travel except to a few countries on the UK government’s “green list,” for travel, the status of which is subject to change. [5,6]
Against that background, the success of the vaccination rollout has generated optimism that the end of the lockdown may be in sight, even if it is a little later than planned. The new secretary of state for health and social care, Sajid Javid, has suggested that restrictions are likely to be lifted on 19 July. It is anticipated that unrestricted international air travel will resume at some point soon. Airline and tourism industries are preparing to benefit from the public’s yearning to travel overseas, and hope to return to pre-covid levels of profitability as quickly as possible. But this assumption appears simplistic, when set against two challenges. Firstly, in many low and middle income countries, covid-19 infection is rampant and vaccination rates are low, with the potential of new variants emerging.  Secondly, of even greater concern, is the fact that the pandemic is merely a “dress rehearsal” for what awaits us as the climate emergency progresses. 
With the risk of prolonging the pandemic, and with only a decade left to avert the worst impacts of the climate emergency, we argue that it is premature to re-open international travel to large numbers of travellers at present and to plan for even greater volumes of air travel in the future.
The risks posed by unrestricted international air travel will persist unless we have a successful worldwide immunisation programme, preferably with a vaccine which will have components covering possible variants. But restrictions to travel will be unwelcome to the aviation industry, to businesses, and to a large proportion of the general public who long to travel abroad once more. Indeed at least 97 airport authorities, in the UK and around the world, have tabled proposals to expand their operations in a bid to return to profitability, in spite of a recommendation to the contrary from the Climate Change Committee, the UK’s independent advisor on tackling climate change. A further 49 new airports are already under construction around the globe. [9,10]
The UK government recently hosted the G7 summit which addressed the twin themes of global recovery from the pandemic and climate emergency, but disappointingly, failed to match the scale of the challenges with clear action.  In November 2021, the UK will host the 26th UN Climate Change Conference of the Parties (COP26), and is expected to demonstrate leadership in the stated objective to “stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” 
To this end the International Energy Authority has proposed a roadmap to decarbonise the global economy.  Aviation contributes only around 2.5% of global emissions (5% percent of emissions in the UK, where around half the population fly in any given year), but is the most carbon-intensive mode of travel and one of the most difficult sectors to decarbonise due to lack of viable alternatives to aviation fuel or improving aircraft efficiency.  Offsetting is also not a practical option given that net zero target needs to be achieved in the next few decades. Consequently, reducing passenger demand is a significant component of the roadmap, with options to achieve this including advocacy on lifestyle, pricing, and limiting the capacity of airports. The “Zoom boom” has already reduced demand for business travel (another lesson from covid-19), but reducing demand for leisure travel will be a challenge and this is where government leadership will be most required.  There are some encouraging signs; the French Government has taken steps to replace short haul internal flights with train journeys where possible. 
Aviation has fallen through the nets of past global climate policy initiatives, but in the UK, that changed following the government’s announcement in April 2021 that international aviation and shipping would be included in the climate law, requiring these sectors to be part of the UK’s 2050 net zero emission target.  This is a big step forward in holding the aviation industry to account for its emissions, but also highlights a second point: it is unrealistic to expect the industry to restrict its own activity, even where such restrictions are essential to global health and security. Governments and regulators must have the courage to help achieve these difficult decisions, even in the face of opposition from the industry and their supporters among politicians, the public, and some sections of the press. No industry can be exempt from contributing to net zero targets, if we are to hope to avert climate catastrophe and reduce the risks of future pandemics. Airport expansion has no place in planning for a safer future.
Jangu Banatvala, emeritus professor of clinical virology, School of Medicine and Dentistry, Kings College London.
Peter Muir, consultant clinical scientist, Public Health England, South West Regional Laboratory Bristol.
Mala Rao, director, Ethnicity and Health Unit, Department of Primary Care and Public Health, Imperial College London.
Competing interests: Jangu Banatvala is health advisor to Stansted Airport Watch.
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