A formation of the Blue Angels fly over Washington D.C. area, the United States, on May 2, 2020. The U.S. Navy's Blue Angels and U.S. Air Force's Thunderbirds honored frontline COVID-19 responders and essential workers with formation flights over here on Saturday. (Xinhua/Liu Jie)

A formation of the Blue Angels fly over Washington D.C. area, the United States, on May 2, 2020. The U.S. Navy's Blue Angels and U.S. Air Force's Thunderbirds honored frontline COVID-19 responders and essential workers with formation flights over here on Saturday. (Xinhua/Liu Jie)

A formation of the Thunderbirds and Blue Angels fly over the National Mall in Washington D.C., the United States, on May 2, 2020. The U.S. Navy's Blue Angels and U.S. Air Force's Thunderbirds honored frontline COVID-19 responders and essential workers with formation flights over here on Saturday. (Photo by Ting Shen/Xinhua)

A formation of the Thunderbirds and Blue Angels fly over Washington D.C. area, the United States, on May 2, 2020. The U.S. Navy's Blue Angels and U.S. Air Force's Thunderbirds honored frontline COVID-19 responders and essential workers with formation flights over here on Saturday. (Xinhua/Liu Jie)

A formation of the Thunderbirds and Blue Angels fly over the Washington Monument in Washington D.C., the United States, on May 2, 2020. The U.S. Navy's Blue Angels and U.S. Air Force's Thunderbirds honored frontline COVID-19 responders and essential workers with formation flights over here on Saturday. (Photo by Ting Shen/Xinhua)

A formation of the Thunderbirds and Blue Angels fly over Washington D.C. area, the United States, on May 2, 2020. The U.S. Navy's Blue Angels and U.S. Air Force's Thunderbirds honored frontline COVID-19 responders and essential workers with formation flights over here on Saturday. (Xinhua/Liu Jie)