U.S. COVID-19 deaths surpassed 550,000 on Tuesday, according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University. With the national case count topping 30.3 million, the death toll across the United States rose to 550,073 as of 8:26 a.m. local time (1226 GMT), according to the CSSE data. California topped the U.S. state-level death toll list, standing at 59,030. New York reported the country's second largest death toll of 50,158, followed by Texas with 48,134 deaths and Florida with 33,247 deaths, the CSSE tally showed. States with more than 17,000 fatalities also include Pennsylvania, New Jersey, Illinois, Georgia, Ohio, Massachusetts and Michigan. The United States remains the nation worst hit by the pandemic, with the world's highest caseload and death toll, accounting for more than 23 percent of global cases and nearly 20 percent of global deaths. U.S. COVID-19 deaths reached the grim milestone of 500,000 on Feb. 22  Also read: US tops 30 million confirmed cases of COVID-19 The Transportation Security Administration reported a new air travel record during the pandemic, with more than 1.5 million people screened at U.S. airports on Sunday. U.S. health experts warned that the busy air travel nationwide amid this spring break may be one reason behind the recent spike in new cases. Also read: Global Covid-19 cases surpass 124 million   An updated model by the Institute for Health Metrics and Evaluation at the University of Washington projected a total of 600,195 COVID-19 deaths in the United States by July 1, based on the current projection scenario.