From his towering vantage point, a few thousand feet up in the blue holiday sky, the Curtiss J-4 biplane's pilot spotted the West Side Tennis Club's classic Tudor clubhouse and began his descent.

This assignment was a cakewalk for Navy Lt. James Murray Grier, a Philadelphian who had grown up on North 11th Street and become a decorated World War I pilot in France's famed Lafayette Escadrille.

Grier's lone passenger that Labor Day afternoon, Sept. 6, 1920, was Army Sgt. Joseph P. Saxe. The nation's top military photographer, Saxe was an adventurous veteran of battles in the Philippines and China. Earlier that summer he'd miraculously survived a plunge into New York Harbor after falling from a plane while shooting an America's Cup race.

But their luck would soon expire. Minutes later both would die in a crash that nearly became one of the worst and most bizarre tragedies in American sports history.

In 2018, blimps and planes routinely provide aerial views of sporting events. In 1920, though, the practice – for the photographer, the pilot, and the crowd below – was extremely risky.

On that sultry September afternoon, Grier and Saxe took off from Long Island's Mitchel  Field. Their assignment was to photograph the men's final of the 1920 U.S. Tennis Championships.

The Army, its numbers depleted after World War I, wanted photos of sporting events for a new recruitment campaign.

Grier's aging biplane first appeared above the Forest Hills, N.Y., club — the women's championship would be played later that month at Philadelphia's Germantown Cricket Club — during the second set of a match between defending champion Bill Johnson and 1919 runner-up Bill Tilden.

That pairing was extremely appealing to tennis fans in a nation that rapidly was becoming sports-crazed. The 5-foot-8 Johnson and 6-2 Tilden – "Little Bill" and "Big Bill" — were not only America's two best players, but a year earlier they had shared the world's top ranking. Earlier that summer, Tilden had won his first major, at Wimbledon.

More than 12,000 spectators were packed into the makeshift grandstands that organizers had hurriedly constructed around the exclusive club's main court. And they were annoyed.

Like golf, tennis was as hidebound as the aristocrats who then played and most closely followed the sport. Any intruder into the genteel world that their well-tended grass courts symbolized, especially one so obvious as a noisy, smoke-belching airplane, was an abomination.

As Johnson was evening the match with a 6-1 second-set triumph, Grier dipped the biplane low over the crowd so that Saxe, leaning out an open cockpit door, could get an ideal view. They did it again and again, the plane diving so low on its fourth pass that one spectator later said those in the upper seats "might almost touch it."

"Each time the plane swooped near the stadium and the motor roared, angry spectators turned their gaze from the on-court action below to the noisy distraction above," writes Allen M. Hornblum in his new biography of Philadelphia's Tilden, America's Colossus: Big Bill Tilden and the Creation of Modern Tennis.

Through it all, Tilden and Johnson played on.

Then, with Tilden ahead, 3-1, in the third set, Grier, the son of a prominent Philadelphia doctor, maneuvered the aircraft back toward the stadium, apparently preparing for a fifth descent.

That's when the drone of its motor suddenly, ominously, ceased.

"Instinctively I looked up," Tilden later wrote, "and was horrified to see the plane wobble and plunge downward."

Some news accounts estimated the altitude at which the plane stalled at 800 feet. Whatever, it spiraled downward, picking up speed in the free fall. Spectators screamed.

No one will know whether Grier was able to maneuver the doomed craft away from the stands. But it crashed just 200 feet away, undoubtedly sparing countless lives.

"[I] felt the shock through the earth," Tilden recalled.

Many in the crowd rushed to the wreckage, where they saw the bodies enmeshed in twisted metal. The impact drove the aircraft's motor three feet into the ground.

Not knowing how – or even if — they should proceed, Tilden and Johnson walked in stunned silence toward the umpire's chair. The official asked if they could continue.

"Yes," Johnson said.

"I'm ready,"  Tilden replied.

Later, Tilden called the decision "heartless, almost indecent," but others believed the completion of the match may have prevented a panic among the spectators.

Tilden, raised just outside the gates of Germantown Cricket, eventually defeated his younger rival. The five-set victory launched the elegant athlete on a career of unprecedented dominance.

Voted the greatest tennis player of the first half of the 20th century, he won seven U.S. titles during the '20s, a decade when sports heroes like him leaped into the foreground of American culture. Overall, Tilden captured 12 Grand Slam singles titles despite never playing in the Australian championships.

That same afternoon, 735 miles to the west in a hastily built Benton Harbor, Mich., stadium, there was another collision of technology and sports tradition, this one not tragic but perhaps ultimately more significant.

Detroit station WGN, which had obtained one of the nation's first radio licenses just weeks before,  provided a rudimentary broadcast of the heavyweight championship fight between Jack Dempsey and Billy Miske, the first sporting event on the new medium.

The following summer, the first baseball game – an 8-5 Pirates victory over the Phillies — would be aired. Soon American sports were changed forever.

Dempsey knocked out Miske in the third round that day. Along with Tilden, Babe Ruth, Bobby Jones, and Red Grange, he would be one of the cluster of  sports legends to arise in the 1920s.

Meanwhile, though they'd flown high in their time on earth, and almost certainly too low on the day they died, Grier and Saxe became  historical footnotes.

They would be quickly forgotten, even by those whose lives the Philadelphia pilot might have saved alongside Forest Hills' emerald lawns on that long-ago Labor Day.