This egg-shaped monument in Ireland is one of the most important aviation sites ...

(CNN) — Roughly 2,500 transatlantic flights soar through the skies each day, whisking passengers over the ocean in less than six hours.

June 15, 2019, marks 100 years since British aviators John Alcock and Arthur Brown completed the first nonstop transatlantic flight.

It wasn't 100% intentional; from the sky, the green mud looked like a flat field.

Alcock and Brown might have semi-crash-landed -- but regardless, the pioneering pilots had completed a monumental feat, paving the way for transcontinental aviation as we know it today.

"It is a massive, massive achievement," says Peter Collins, heritage manager at aerospace manufacturer Rolls-Royce. "The flight in 1919, that's only 16 years after first powered flight."

Today, the duo's landing site doesn't reveal a lot about its aeronautical past. Alcock and Brown's achievement is commemorated by an unusual egg-like memorial, surrounded by grassy hills, sweeping views and plenty of sheep.

Aviation milestone

The area is also home to the ruins of the world's first permanent transatlantic radio station, which once employed hundreds of people to transmit news across the water.

As well as the enigmatic egg, there's a more conventional memorial in recognition of Alcock and Brown's flight: an airplane wing that's closer to the road.

The whole area is a stunning spot for an aviation-themed pilgrimage -- just don't expect a museum, there's just the monuments, and a few signs telling the story of Alcock and Brown's achievement.

The British pilots set off from St John's in Newfoundland, Canada, in a Vickers Vimy biplane powered by two Rolls-Royce Eagle engines, made at the Rolls-Royce factory in Derby, England -- where engineers still manufacture airplane parts today.

This production line has its roots in British military requirements during World War I. When the war ended in 1918, there were many Eagle engines still in production, so the manufacturers were keen to prove aviation had a place in peacetime.

The British Daily Mail newspaper ran a competition promising £10,000 to the first pilots who crossed the Atlantic without stopping in less than 72 hours (around $641,000 in today's money).

The British team headed to Newfoundland in June 1919 to give it a shot. Photographs depict the engine being ferried to the departure spot in a horse and cart -- a true past-meets-future moment.

It was a team effort, but once they were up in the air, Alcock and Brown navigated their way across the ocean with no air traffic control and no GPS. Imagine not just the threat of turbulence, but being completely exposed to the elements, and to birds.

The pilots kept warm via custom-made Burberry heated suits.

"When they landed in Ireland, it was their first sight of landfall, because, of course, they use [navigation instruments] like sextants," says Collins.

Alcock and Brown originally planned to travel on to London, but the plane wouldn't budge from the bog. Still, they'd pipped the other teams to the post, successfully completing the first ever, non-stop transatlantic flight.

The duo completed the journey in 16 hours and 12 minutes, grabbing the prize money and sharing it with the Rolls-Royce and Vickers engineers who'd built the aircraft.

For the aircraft manufacturers, it was a marketing, as well as technological, triumph.

"The crossing of the Atlantic by aviation was seen as a real [Marco Polo-style] adventure that could be achieved at that time -- showing that aviation isn't just a 'fly by night' sort of activity. It's here to stay," says Collins.

Still, commercial aviation didn't take off properly right away, says the historian.

"That mindset change doesn't really happen until after the Second World War, in the '20s and '30s. Although there were scheduled flights and aviation is developing and growing, it's not massive [...] It's still for the well-off people," he says.

"Quite often in history, we look for cataclysmic changes," says Collins, but the reality is that a significant event will occur, and "then the aftermath takes a long time to cope with what has happened. And that's why I think that happened with the Alcock and Brown flight."

Marking the occasion

Keith Ewing, a retired university teacher from Minnesota, takes college students on organized trips to the Alcock and Brown monument in Derrigimlagh.

He says seeing the site is pretty incredible.

"You're standing on top of this bog and the bog has been there for truly just thousands of years," he tells CNN Travel.

"And unchanged, really, since Alcock and Brown crash-landed there. It sort of forces that juxtaposition of time and human endeavor and natural endeavors -- and you see it in a different way, you experience it differently."

The egg-shaped monument is visible from pretty faraway. There's also a spot where looking through glass panels allows you to glimpse what the biplane actually looked like silhouetted against the landscape, bringing the past into the present.

"That's what I enjoy about it -- and to think of these guys flying at 110 miles an hour across the Atlantic, you think of how cold it was," says Ewing.

He adds that his accompanying students have similar reactions.

"They're sitting there going: 'Whoa, wait a minute. 110 miles an hour? There's no cockpit? How did they do that? Man, they did some crazy things back in those days.'"

Ewing used to work for an airline and sought out the monument -- he's fascinated by how technology impacts our lives.

Meanwhile photographer Donal Healy, who visited Derrigimlagh back in summer 2018, stumbled across the site more accidentally.

He was driving in a VW camper van with his girlfriend, on a mission to complete the Wild Atlantic Way.

Immediately, he says, the couple were struck by the atmosphere of this hidden gem.

"The site is very unusual, it has an eerie, almost haunted feel," he says.

"I'm from the west of Ireland originally and, for me, Connemara is as Irish as Ireland gets. It was mid-July and the sun was splitting the stones so all the turf was lifted, bone-dry and sat in mounds on either side of the road waiting to be collected."

As for the Alcock and Brown monument, he says it's simultaneously memorable and unassuming.

"It's a whitewashed concrete lump around about the spot where they crashed. There are some photos and a brief history. It's a very quiet spot and there is no visitor center, just an eccentric local man selling tea out of a trailer in the car park."

Healy found himself struck by the pilots' bravery against the odds and reconsidering the ease of present-day transatlantic flight.

The flight is commemorated outside of Ireland too. Over in Canada there are three monuments that commemorate the flight's beginnings in Newfoundland. At London's Heathrow Airport, there's a memorial statue of the duo, built in 1954, that's currently in Clifden in Galway for the centenary celebrations.

Speaking at the Rolls-Royce factory in Derby, Caroline Day, head of marketing, strategy and future programs, says the company's constantly looking for the next step on a road of innovation.

"Over 100 years, turboprops, piston engines, jet engines, supersonics, flying across the Atlantic -- you know, we've pretty much done it all."

The next step, she says, is perfecting electrification -- and achieving ambitious environmental goals.

Wherever transatlantic flight goes next, it wouldn't be possible without the June 15, 1919 flight.