More fuel-efficient planes have halved commercial flights emissions over the past 30 yearsand we are partnering with NASA to develop and test a full-scale demonstrator airplane that could inform the designs of future airplanes to be as much as 30% more fuel-efficient.

However, achieving net zero in the next 28 years will also require rethinking which non-fossil energy sources should power the aircraft itself.

The problem

When it comes to changing airplanes energy carriers, safety and the laws of physics rule. Finding renewable energy alternatives with the same energy density and volumetric efficiency as fossil fuels is difficult.

Today, flights over 1,000 miles account for 80% of the industrys emissions. New batteries will enable electric aircraft to be developed for short-haul travelbut batteries weigh too much for longer flights.

Many challenges must be overcome before hydrogen-powered long-haul planes can safely complete flights, refuel, and leave for their next destinations within an hour as most do today

Loading the smallest molecule in the universe into aircraft is tricky. Due to their small size and required cryogenic conditions, hydrogen molecules can leak through minute pores of welded seams and be absorbed into metal, since hydrogen and cooler temperatures can make metal brittle. Airports will need new infrastructure and training to safely load and handle the frigid fuel that must be chilled at -423 degrees Fahrenheit.

Storing hydrogen poses equally complicated challenges. Planes will have to be redesigned since hydrogen requires more space, as well as cryogenic conditions. Hydrogen takes up to four times the volume as jet fuel.

Hydrogen must be proven every bit as safe and practical as traditional jet fuel to be viable. That means governments will need to establish an alternative set of airworthiness requirements.

What the numbers say about reaching net zero by 2050

NASAs inspiring Artemis 1 mission reminds us of valuable lessons for hydrogen aircraft and what it means to achieve net zero emissions by 2050.

The Space Launch System rocket we developed with NASA used supercooled hydrogen to launch the uncrewed Orion spacecraft. It is the latest in a long line of spacecraft and test aircraft to prove hydrogen-powered flight possible over the past half century. With NASA, we flew on hydrogen when Apollo 11 took humanity to the moon in 1969.

Using hydrogen directly in commercial aircraft requires substantial changes to both the aircraft and the infrastructure around it. Learning how to safely and efficiently load, store, fly and scale hydrogen-powered aircraft will be the challenge of a generation of engineers.

By contrast, short and long-range aircraft can fly on sustainable aviation fuels, or SAF, which are non-fossil certified variants of traditional petroleum jet fuel. The primary materials can be sustainable bio-based waste sources like plant oils and cooking oil, industrial capture, or even the electric grid itself. SAF can be dropped into todays aircraft and infrastructure to mitigate emissions immediately by up to 80% over their life cycle.

While flying on hydrogen does not emit carbon, its production often does. Since most hydrogen today is produced from fossil fuels, truly reducing emissions by flying on hydrogen will also require a wholesale transformation of the energy industry to ensure sufficient so-called green hydrogen produced from renewable electricity exists for aviation. Aviation has to compete with other sectors for green hydrogen as it becomes available.

Even then, it is arithmetically impossible to replace the worlds fleets with hydrogen-powered airplanes in time to meet the industrys 2050 target.

By the late 2030s, we estimate more than 40,000 non-hydrogen commercial jets will be in service. Each will last decades. Given that the most airplanes ever produced around the world in a year so far have been about 1,800, we cant just switch overnight to hydrogen. Emissions from those aircraft will need to be mitigated with SAF.

Hydrogen-powered aircraft may make a small contribution to moderating emissions in 2050. And while research today may develop solutions for the latter half of the century, it must also consider the 2050 challenge at hand.

To ensure future generations can continue to fly and enjoy the other global benefits the aerospace industry contributes to a strong economy, aviation must focus on developing and scaling SAF. Advances in the science and engineering of complex hydrogen propulsion technologies should be pursued, but likely apply to the longer term.

Our founder Bill Boeing once said, Let no new improvement in flying and flying equipment pass us by. As the Artemis 1 mission shows, our industry achieves the seemingly unattainable. The world must scale sustainable aviation fuels that can be dropped into existing aircraft today, while exploring decarbonized propulsion technologies like hydrogen and electricity that can make an impact in the second half of the century.

Christopher Raymond is the Chief Sustainability Officer of Boeing

The opinions expressed in Fortune.com commentary pieces are solely the views of their authors and do not necessarily reflect the opinions and beliefs of Fortune.

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Really, that money would be better spent on lining workers pockets.

A new study surveyed 626 business school students with an average age of 29 across 72 different countries and found that salary was the single most important factor when job hunting.

This was universally true across both for men and women in every country and across all industries surveyed by Jan Malte Jeddeloh from ESMT Berlin, who performed the research for his master of management thesis.

Instead of office gimmicks or flashy incentives, the research reveals that young workers really arent that different to previous generations; they value traditional standards from their workplacelike a well-paid full-time job.

The 5 most important factors for young people when choosing an employer

1. Salary

Most of those surveyed want to be paid more than the industry average. Jobs with below-industry- average salary were disregarded by respondents.

2. Type of contract

Respondents favored permanent contracts, over short fixed-term contracts or temporary employment. 

3. Remote work

In the aftermath of the pandemic, young people want the flexibility to be able to work from homeor from a location of their choicefor at least, some of the working week. This was actually more important to respondents in Western Europe and North America than the type of contract on offer.

4. Company reputation 

Reputation matters. And if you thought that those negative Glassdoor reviews werent important, think again. Applicants do look atand take into accountcompany reputation. More specifically, as well as prestige, young would-be workers take into account your firms reputation for sustainability and social responsibility.

5. Status

Globally, participants in the study would rather go for a managerial position than have a manager. Perhaps unsurprisingly, status matters more to men. The position the employee has within the company didnt make the top five criteria young women look for in employersthey value purpose more. 

What this means for businesses

For a few years now, Generation Z has been joining the job market, and managers are still asking themselves how they can manage and retain the new generation, research author Malte Jeddeloh says while pointing at the great resignation as a mismatch in what employers think their workers want, versus what workers actually want.

The research indicates that classic work values like salary and contract security are still decisive for the younger workforce, which might be connected to the unstable worldwide situation and the resulting need for security, Malte Jeddeloh adds. 

In comparison, the size of the company, bonus scheme, DEI initiatives, working hours, and whether the work was routine or varied, mattered the least to the young workers surveyed. 

Respondents from Western countries and female participants ranked new work attributes, like remote working, purpose, inclusion, and work-life balance, as more important than did men and respondents from Asian countries. Meanwhile, male participants typically placed more value on classic work attributes like the type of contract, salary, and status of job offers. Although, classic work values like hours and bonuses were also attractive to female participants. 

Nevertheless, salary stayed with a clear lead ahead of all career attributes in terms of importance. This was also true for Gen Z respondents (those born between 1997 and 2012). In light of the global crisis theyve witnessed in their short-lifetime, GenZ also cares about employer propositions around social and sustainability issues. 

The results suggest that aside from offering a generous pay packet, employers could alter their offerings slightly in job ads to be more (or less) attractive to young men, women, or specifically, Gen Z.

The report adds that the findings highlight the importance of transparency when it comes to company values and job adverts. 

The entire process, the company, the propositions, and everything surrounding an employer should be as transparent as possible, Malte Jeddeloh writes.

For example, a company with an openly competitive salary will be instantly appealing to candidates. But job offers that arent in line with the industry averageand dont open about itwill get found out and potentially called out later down the application process.  

Comparison of jobs is easy in todays world; thus, a lack of transparency will lead to a lack of trust, Malte Jeddeloh adds.

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Hong Kongs strict anti-COVID-19 measures and diminishing freedoms have clearly impacted the city and the people in it, Greg May said, citing the departure of roughly 15,000 Americans as one of the outcomes. He said about 70,000 Americans and 1,300 U.S. companies are currently present in Hong Kong.

In a video address late Wednesday to the U.S. Center for Strategic & International Studies, May also said worries remain over Hong Kongs reputation as a business center which depends on adherence to international standards and the rule of law.

Among those concerns was an interpretation last month by the standing committee of National Peoples Congress, Chinas legislature, that could further undermine the independence of Hong Kongs judiciary system by expanding the Hong Kong executive branchs authority to make decisions affecting cases without judicial oversight, May said.

The standing committee ruled that Hong Kongs courts need the approval of the territorys chief executive or a separate committee to allow foreign lawyers to take part in national security trials.

That came after Hong Kong leader John Lee, who is under U.S. sanctions, asked Beijing to make a ruling that could effectively block jailed pro-democracy publisher Jimmy Lai from hiring a British lawyer to represent him.

Lai was arrested in 2020 during a crackdown on the citys pro-democracy movement that led Beijing to impose a sweeping National Security Law on the city. He is fighting collusion charges and faces up to life in prison if convicted.

May said that in light of the standing committees ruling and other developments, companies should be aware that the risks faced in mainland China are now increasingly present here in Hong Kong.

The National Security Law and actions taken by Beijing and Hong Kong authorities may negatively impact company staff, finances, legal compliance reputation and operations, he said.

Hong Kongs reputation as a free global financial center could be further harmed if more of the best and brightest leave the city, he said, referring to the decision by many Hong Kong citizens to move abroad after 2020.

The citys government should cease its dismantlement of Hong Kongs democratic institutions, autonomy and rule of law, release those held unjustly and respect human rights for all, May said.

In a response, the Chinese Foreign Ministrys office in Hong Kong said May slandered the rule of law and freedom in Hong Kong and deliberately discredited Hong Kongs business environment.

May recklessly trampled on the basic principle of not interfering with a places domestic affairs under international law and international relations, it said in a statement posted online.

He supported those who have opposed China and disrupted Hong Kong, and also badmouthed Hong Kongs development prospects, the statement said.

The U.S. and other major democracies have been critical of Chinas crackdown on political freedoms in the former British colony, which was handed back to China in 1997 with a promise by Beijing to keep Western-style liberties under a one country, two systems framework.

Hong Kong is among a raft of issues that have sent ties between Beijing and Washington to their lowest level in years, including technology and trade, human rights, threats against Taiwan, and Chinas claims in the South China Sea.

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Some politicians and a few public health practitioners have argued that COVID-19 deaths are overcounted. For instance, a January 2023 opinion piece in The Washington Post claims that COVID-19 death tallies include not only those who died from COVID-19 but those who died from other causes but happened to have COVID-19.

Most scientists, however, have suggested that COVID-19 death tallies represent underestimates because they fail to capture COVID-19 deaths that were misclassified to other causes of death.

We are part of a team of researchers at Boston University, University of Minnesota, University of California San Francisco and other institutions who have been tracking COVID-19 deaths since the beginning of the pandemic. A major goal for our team has been to assess whether the undercounting of COVID-19 deaths has occurred, and if so in which parts of the country.

Examining excess deaths

One way to examine the issue is to look at what population health researchers call excess mortality. Its a measure which, in this case, compares the number of deaths that occurred during the pandemic to the number of deaths that would have been expected based on pre-pandemic trends.

Excess mortality captures deaths that arose from COVID-19 directly or through indirect pathways such as patients avoiding hospitals during COVID-19 surges. While determining a cause of death can be a complex process, recording whether or not someone died is more straightforward. For this reason, calculations of excess deaths are viewed as the least biased estimate of the pandemics death toll.

As a general rule of thumb with some important caveats that we explain below if there are more COVID-19 deaths than excess deaths, COVID-19 deaths were likely overestimated. If there are more excess deaths than COVID-19 deaths, COVID-19 deaths were likely underestimated.

In a newly released study that has not yet been peer-reviewed, our team found that during the first two years of the pandemic from March 2020 to February 2022 there were between 996,869 and 1,278,540 excess deaths in the U.S. Among these, 866,187 were recognized as COVID-19 on death certificates. This means that there were between 130,682 and 412,353 more excess deaths than COVID-19 deaths. The gap between excess deaths and COVID-19 deaths was large in both the first and second years of the pandemic. This suggests that COVID-19 deaths were undercounted even after the pandemics chaotic early months.

Major studies have also concluded that excess deaths exceeded COVID-19 deaths at the national level during the first two years of the pandemic. And preliminary analyses by our team have found that the gap between excess deaths and COVID-19 deaths has persisted into the third year of the pandemic. This suggests that COVID-19 deaths are still being undercounted.

Making sense of the discrepancy

Explaining the discrepancy between excess deaths and reported COVID-19 deaths is a more challenging task. But several threads of evidence support the idea that the difference largely reflects uncounted COVID-19 deaths.

In a recent study, we found that excess deaths peaked immediately before spikes in reported COVID-19 deaths. This was the case even for excess deaths associated with causes like Alzheimers disease that are unlikely to rapidly change due to patients avoiding hospitals or other changes in behavior during the pandemic.

This finding aligns with the observation that COVID-19 deaths may go unrecognized and be misclassified to other causes of death at the beginning of COVID-19 surges. At this time, COVID-19 testing may be less frequent in the community, among medical providers and among death investigators. If excess deaths were not caused by COVID-19, they would instead either remain relatively constant during COVID-19 surges or they would peak afterwards when hospitals were overcrowded and deaths may have resulted from health care interruptions.

Excess deaths related to external causes of death such as drug overdose also increased during the pandemic. However, a preliminary study found that the scale of this increase was small relative to the overall increase in excess deaths. So deaths from external factors alone cannot explain the gap between excess and COVID-19 deaths.

This evidence is worth considering in light of the prominent opinion piece in the Washington Post mentioned earlier, which suggests that the U.S.s tally of COVID-19 deaths is a substantial overcount. The author argues that in some hospitals, widespread COVID-19 testing has led patients with COVID-19 who died of other causes to still have COVID-19 included as a cause on their death certificate. There is a fundamental misunderstanding, however, in generalizing these hospital deaths to the entire country.

One reason this overgeneralization is flawed is because hospital deaths are distinct from out-of-hospital deaths. In out-of-hospital settings, COVID-19 testing is often lacking and death investigators have less training and less information about the deceased. In fact, our research suggests that COVID-19 deaths are largely undercounted in out-of-hospital settings.

Investigative reporting among coroners in rural areas has also revealed significant variability in out-of-hospital cause of death assignment. Some coroners have even gone on record to state that they do not include COVID-19 on death records if it contradicts their own political beliefs or if families wish for it to be omitted.

The other problem with the overgeneralization is geographic. Our preliminary study demonstrates that excess deaths exceeded COVID-19 deaths in the vast majority of counties across the U.S. In particular, counties in the South, the Rocky Mountain states and rural areas had many more excess deaths than COVID-19 deaths. This suggests that COVID-19 deaths were likely undercounted in these areas.

The idea that COVID-19 deaths are sometimes overreported is, to a very limited extent, supported by our analyses. A select number of large and medium-sized metro areas in New England and the mid-Atlantic states have had more COVID-19 deaths than excess deaths. But most of the country has not followed the patterns of this small group of counties.

While it is possible that some deaths assigned to COVID-19 in New England and the mid-Atlantic states were not actually caused by COVID-19, other explanations are also possible. First, COVID-19 mitigation efforts could have prevented deaths in these areas via pathways unrelated to COVID-19, reducing excess deaths. For example, some people living in wealthy, urban counties had the privilege to work from home and avoid household crowding, which may have reduced their risk of dying from flu. Flu is typically responsible for as many as 50,000 deaths each year.

In fact, the 2020-2021 flu season was minimal, likely because of social distancing. Another possible explanation is that later in the first two years of the pandemic, there may have also been fewer deaths than expected in some areas because some of the least healthy people in the area had already died of COVID-19. These alternative explanations imply that, even in those New England and mid-Atlantic counties where more COVID-19 deaths were recorded than estimated excess deaths, many COVID-19 deaths may still have occurred even as other kinds of deaths decreased.

Why it matters

Ultimately, figuring out how many people have died as a result of the COVID-19 pandemic is a major scientific undertaking that has significant political importance. Knowing how many people died and where these deaths occurred has widespread implications for informing how current pandemic response resources are allocated and for preparing for future public health emergencies.

As a result, in our view, it is critical that the scientific community carefully reviews the rigor of the science behind the counting of COVID-19 deaths. Given the intense politicization of the pandemic, claims of overcounting or undercounting need to be made cautiously.

Finally, research by our team and investigative reporting conducted in partnership with our team has found that the undercounting of COVID-19 deaths is significantly more common in Black, Hispanic and Native American communities as well as low-income areas. Claims that COVID-19 deaths have been overcounted undermine efforts to reconcile the undercounts in these communities and to ensure resources are being allocated to those most affected. For example, if a person does not have COVID-19 assigned as a cause on their death certificate, their family is ineligible for pandemic social programs such as the FEMA funeral assistance program.

To understand where the U.S. public health system has succeeded and fallen short during the pandemic, a full accounting of deaths caused by COVID-19 is needed. More than that, families, friends and loved ones of those who have died so far also deserve to know the true toll that COVID-19 has taken.

Andrew Stokes is Assistant Professor of Global Health, Boston University; Dielle Lundberg is Research Assistant in the Department of Global Health, Boston University; Elizabeth Wrigley-Field is Assistant Professor of Sociology, University of Minnesota, and Yea-Hung Chen is Research Data Specialist in Epidemiology and Biostatistics, University of California, San Francisco.

This article is republished from The Conversation under a Creative Commons license. Read the original article.