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Washington, Jan 2: The number of people killed in large commercial airplane crashes fell by more than 50% in 2019 despite a high-profile Boeing 737 MAX crash in Ethiopia in March, a Dutch consulting firm said on Wednesday. Aviation consulting firm To70 said there were 86 accidents involving large commercial planes - including eight fatal incidents - resulting in 257 fatalities last year. In 2018, there were 160 accidents, including 13 fatal ones, resulting in 534 deaths, the firm said.

To70 said the fatal accident rate for large airplanes in commercial passenger air transport was just 0.18 fatal accident per million flights in 2019, or an average one fatal accident every 5.58 million flights, a significant improvement over 2018. The fatality numbers include passengers, air crew such as flight attendants and any people on the ground killed in a plane accident

Large passenger airplanes in the study are aircraft used by nearly all travelers on airlines worldwide but excludes small commuter airplanes in service, including the Cessna Caravan and some smaller turboprop airplanes, according to To70.

On Dec. 23, Boeing's board said it had fired Chief Executive Dennis Muilenburg after a pair of fatal crashes involving the 737 MAX forced it to announce it was halting output of its best-selling jetliner. The 737 MAX has been grounded since March after an October 2018 crash in Indonesia and the crash of a MAX in Ethiopia in March killed a total of 346 people.

To70 said the aviation industry spent significant effort in 2019 "focusing on so-called 'future threats' such as drones." But the MAX crashes "are a reminder that we need to retain our focus on the basics that make civil aviation so safe: well-designed and well-built aircraft flown by fully informed and well-trained crews."

The Aviation Safety Network said on Wednesday that, despite the MAX crash, 2019 "was one of the safest years ever for commercial aviation." The 157 people killed in March on Ethiopian Airlines Flight 302 accounted for more than half of all deaths last year worldwide in passenger airline crashes.

Over the last two decades, aviation deaths around the world have been falling dramatically even as travel has increased. As recently as 2005, there were 1,015 deaths aboard commercial passenger flights worldwide, the Aviation Safety Network said.

Last week, 12 people were killed when a Fokker 100 operated by Kazakh carrier Bek Air crashed near Almaty after takeoff. In May, a Russian Sukhoi Superjet 100 aircraft caught fire as it made an emergency landing at Moscow’s Sheremetyevo airport, killing 41 people.

The figures do not include accidents involving military flights, training flights, private flights, cargo operations and helicopters.

London, May 20: The current physical distancing guidelines of 6 feet may be insufficient to prevent COVID-19 transmission, according to a study which says a mild cough in low wind speeds can propel saliva droplets by as much as 18 feet.

Researchers, including those from the University of Nicosia in Cyprus, said a good baseline for studying the airborne transmission of viruses, like the one behind the COVID-19 pandemic, is a deeper understanding of how particles travel through the air when people cough.

In the study, published in the journal Physics of Fluids, they said even with a slight breeze of about four kilometres per hour (kph), saliva travels 18 feet in 5 seconds.

"The droplet cloud will affect both adults and children of different heights," said study co-author Dimitris Drikakis from the University of Nicosia.

According to the scientists, shorter adults and children could be at higher risk if they are located within the trajectory of the saliva droplets.

They said saliva is a complex fluid, which travels suspended in a bulk of surrounding air released by a cough, adding that many factors affect how saliva droplets travel in the air.

These factors, the study noted, include the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, how heat and mass are transferred, and the humidity and temperature of the surrounding air.

In the study, the scientists created a computer simulation to examine the state of every saliva droplet moving through the air in front of a coughing person.

The model considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapour and evaporate, along with a grid representing the space in front of a coughing person.

Each grid, the scientists said, holds information about variables like pressure, fluid velocity, temperature, droplet mass, and droplet position.

The study analysed the fates of nearly 1,008 simulated saliva droplets, and solved as many as 3.7 million equations.

"The purpose of the mathematical modelling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the saliva droplets themselves," explained Talib Dbouk, another co-author of the study.

However, the researchers added that further studies are needed to determine the effect of ground surface temperature on the behaviour of saliva in air.

They also believe that indoor environments, especially ones with air conditioning, may significantly affect the particle movement through air.

This work is important since it concerns safety distance guidelines, and advances the understanding of the transmission of airborne diseases, Drikakis said.