Domestic air travel does not appear to have been an important vector for the spread of COVID-19 in the US, study suggests

(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.) Jeff Prince, Indiana University and Daniel Simon, Indiana University (THE CONVERSATION) Fear of flying and catching COVID-19 led to a massive decline in air travel in 2020. But an interesting question emerges: How much did air travel contribute to the early, and uneven, spread of COVID-19 in the U.S.? In a previous study currently undergoing peer review, we looked at the effect of air travel from Italy and China on the early spread of COVID-19 in the U.S. and found while flights from Italy were an important source of exposure, ones from China were not. Experts have offered many explanations for why the virus spread so unevenly in the U.S. and elsewhere, ranging from population density to public transportation. We are economics researcherswith experience studying air travel. In a recent study that is beginning the peer review process, we examine whether air travel from early COVID-19 hot spots in the U.S. spread the virus to other parts of the country. The answer is no. Ready for takeoff? The question has recently taken on added importance. With the pace of vaccinations increasing and COVID-19 cases falling, air travel is increasing. Nearly 15% more travelers flew in February than in January. At the same time, the latest guidelines from the Centers for Disease Control and Prevention, updated March 23, 2021, still recommend to delay air travel. This includes those who are vaccinated. The recommendation may be based on the fact that case numbers increase after mass travel, but it is not clear if this relationship is due to air travel per se. To examine whether passengers from COVID-19 hot spots spread the virus to other parts of the U.S., we studied whether counties receiving more passengers from COVID-19 hot spots during the first quarter of 2020 experienced higher COVID-19 infection and death rates during the first wave of the pandemic than counties receiving fewer passengers from COVID-19 hot spots. For our purposes, we determined the first wave ended around May 31, 2020. Our results show that passengers traveling from COVID-19 hot spots at the onset of the pandemic did not spread the virus across the country during the first wave of the pandemic. These results suggest to us that requiring negative COVID-19 tests for airline passengers may not be necessary. Indeed, they may be harmful, if they cause people to drive more. Prior research that one of us conducted showed that after 9/11, increased airport security procedures reduced the demand for air travel. The inconvenience from the additional security, combined with a fear of another terrorist attack on a plane, led many travelers to substitute driving for flying, which resulted in an increase in driving fatalities. In addition, our results suggest that banning domestic air travel may not help to slow the spread of infections. Connecting flights to COVID-19? In our study, we link data on airline travel with county-level data on COVID-19 cases and deaths. We wanted to find out: Did counties with more arrivals from early COVID-19 hot spots ‘” New York City, Boston, New Orleans and Detroit ‘” experience more COVID-19 cases or deaths during the first wave of the pandemic? There are two important challenges in trying to assess the relationship between airline travel and the spread of COVID-19. The first is something called reverse causality: The number of travelers to any area in the U.S. will likely be influenced by the number of confirmed cases and deaths in that metro area. Not many people want to travel to a location experiencing a COVID-19 outbreak.