The risk of exposure to COVID-19 whilst (on a flight) after all passengers test negative 72 hours in advance of your flight is less than 0.1 percent

According to Delta Airlines, "The risk of exposure to COVID-19 whilst (on a flight) after all passengers test negative 72 hours in advance of your flight is less than 0.1 percent". Another reason why US can open travel borders safely". You can read the full Delta press release here. https://news.delta.com/unique-published-study-deltas-pre-flight-testing-significantly-decreases-rate-active-covid-19