TORONTO -- A new study has found that boarding passengers seated at the back of an airplane first may double a person鈥檚 risk of COVID-19 exposure.

The study, conducted by scientists from U.S. colleges including West Florida University and Arizona State University, found that the back-to-front boarding process increases exposure by around 50 per cent compared to randomized boarding.

Major airlines across the world adopted the back-to-front boarding method at the start of the pandemic in early 2020 in an effort to minimizing instances of passengers moving past one another in the aisles.

However, the study's authors reported that back-to-front boarding "is equivalent to one zone per row and can thus be expected to yield increased clustering" in the aisles as passengers wait for those who boarded previously to stow their luggage.

"Our results suggest that the new boarding procedures increase the risk of exposure to COVID-19 compared with prior ones and are substantially worse than a random boarding process," the study's authors wrote.

The study was published Wednesday in the .

The study's authors, who have previously studied the spread of Ebola and SARS on aircrafts, simulated 16,000 various boarding processes and looked at how often people came into close contact with other passengers while boarding.

The study found that back-to-front boarding increased the amount of contact between pairs of seated passengers, and between those in the aisle.

The scientists said airlines could have had a roughly 50 per cent lower risk of infection if they had continued with their pre-pandemic boarding, which typically lets business class passengers board first then those in economy class with passengers sorted into various zones.

Back-to-front boarding policies "do not improve on the old ones in any situation studied here," the study said.

The study noted that most American airlines that adopted back-to-front boarding processes amid the pandemic have reverted back to their traditional method of boarding.

Both Air Canada and WestJet told CTVNews.ca that the companies follow a zone-based boarding system based on the type of ticket purchased, and have done so throughout the duration of COVID-19.

Following the results of the study, the authors say COVID-19 exposure on airplanes could be 鈥渟ignificantly鈥 lowered if airlines prohibited the use of overhead bins to stow luggage, and board the window seat before the aisle seat.

The report added that keeping middle seats empty also reduced the risk of exposure.

"Science-based changes to boarding procedures can decrease COVID-19 infection risk substantially by increasing social distance," the study鈥檚 authors wrote.