WASHINGTON (PTI): The US Air Force and Navy pilots staged a rare joint flyover in three American cities, including Washington, to salute the frontline coronavirus responders and essential workers as the country, the worst hit by the pandemic, fought a grim battle against the "invincible enemy".

Scores of people descended upon the National Mall in Washington on Saturday as the elite pilots of the Thunderbirds and the Blue Angles performed a rare joint flyover over Washington, Baltimore and Atlanta called 'America Strong' to thank the frontline workers, some of whom have sacrificed their lives.

The Thunderbirds and the Blue Angels performed flyovers in Maryland, Virginia and Washington, DC, on Saturday before the aircraft travelled to Atlanta, Georgia. A formation of six F-16C/D Fighting Falcon and 6 F/A-18C/D Hornet aircraft conducted the flyover.

Washington is under a stay-at-home order to slow down the spread of the virus but that did not stop crowds from gathering between the US Capitol and the Washington Monument.

While many people practised social distancing and some wore masks, the sidewalks around the mall were crowded, US media reports said.

The novel coronavirus, which originated from the Chinese city of Wuhan in December last year, has claimed 243,922 lives and infected over 3.4 million people globally, according to Johns Hopkins University data.

The US has the highest number of infections at 1,133,069 and over 67,400 people have died due to the disease.

"During today's tribute, viewers were encouraged to watch the flyover online from the safety of their home quarantine and asked to refrain from travelling to landmarks, hospitals and gathering in large groups," an Air Force official told CNN.

They are the US military's flight demonstration squadrons, and this is the second joint flyover mission being conducted to salute the health care workers, first responders, military and other essential workers risking their lives during the pandemic.

The first joint flight was conducted on Tuesday across New York, New Jersey and Pennsylvania. The joint operation is part of a series of multi-city flyovers being conducted over the next two weeks.

"Beautiful, thank you to our GREAT@BlueAngles and @AFThunderbirds," President Donald Trump, who has described the coronavirus as an" invisible enemy", tweeted.

Trump's wife and first lady Melania Trump also tweeted and said it was a proud moment to see the American military saluting the healthcare and frontline workers.

"Proud to see the #AmericaStrong salute to our healthcare & frontline workers with a spectacular flyover today in Washington, D.C. Thank you to the @AFThunderbirds and @Blueangels for this beautiful display of solidarity," she tweeted.

The White House also joined, taking note of the flypast to honour the country's incredible healthcare workers, first responders and essential personnel fighting the coronavirus.

Manhattan's Dr Sarah Vossoughi, a clinical pathologist at NewYork-Presbyterian/Columbia thanked the US military for showing solidarity with medical professionals like her.

"For them to show us that sign of respect and that sign of honour, for them to do that for us, that makes me feel really special, and it makes it worth it," Vossoughi was quoted as saying by the CBSNews.

"We salute the healthcare workers and first responders who are at the forefront of our nation's fight against COVID-19. They are an inspiration for the entire country during these challenging times and it was an honour to fly for them today," the official handle of the Thunderbirds tweeted.

"We couldn't have asked for clearer weather today while we honoured our frontline healthcare workers and essential employees. We saw you, Washington, D.C., Baltimore, and Atlanta, and we're #InThisTogether! the official Twitter handle of the Blue Angeles tweeted.

The two teams are now planning more "America Strong" flyovers an airborne show of thanks bearing the message, "We're all in this together."