(CNN) — HNL -- MAJ -- KWA -- KSA -- PNI - TKK -- GUM.

That's Honolulu -- Majuro -- Kwajalein -- Kosrae -- Pohnpei -- Chuuk -- Guam.

You'll definitely want a window seat.

Aviation geeks call it "the holy grail of flight routes." For contractors it's one of the world's most picturesque commutes, while for islanders across the region it's a lifeline.

Welcome aboard United Airlines 154, the Island Hopper, a Boeing 737-800 from Honolulu to Guam (and vice versa) which connects seven islands in a truly unique 16-hour flight, four times weekly.

Early morning in Honolulu. Chris Dwyer

This year marks half a century since the route was first flown. Back in 1968 Continental Micronesia was the carrier, starting a service to connect the remote communities across the vast Micronesia region of the Western Pacific.

Today, United flies direct from Guam to Honolulu, seven hours on a 777. But taking this route means missing out on some of the world's most remote and beautiful countries and territories.

The Island Hopper has become a bucket-list must for aviation fans keen to discover the tiny airports dotted across this expanse of Pacific. They're happy to fly the route even though most never get further than the tiny, modest airports along the way.

Most regular passengers tend to do no more than a couple of legs, but many of them have fascinating stories to tell about why they're taking the flight, while multiple factors make this one of the world's most unusual routes.

Four pilots

First Officer Captain Fitz Fitzgerald on one of his last Island Hopper flights before retiring. Chris Dwyer

Firstly, there are four pilots on board. Two fly from Honolulu to Majuro in the Marshall Islands, while the next two then fly the legs from Majuro to Guam.

First Officer Fitz Fitzgerald has just retired after 31 years with United. He's been flying the Island Hopper for four and a half years, after flying 747s for much of his career.

"I jumped at the chance to live on the island (Guam)," he tells CNN Travel during one of his last flights. "I'm from Colorado, it's a long way from the beach! I just fell in love with it."

"I chose to work the Island Hopper almost exclusively. It's a lot of fun, and as a pilot, it's also challenging. This is what flying is all about, from the seat of your pants -- almost. There's no radar, no control towers and GPS gets you within about two miles of the runway, then you've got to find it and line yourself up."

All the smaller islands have short runways with quick turns, while at every stop a fire truck is manned and ready by the side of the runway as they're needed to douse the tires and cool off the brakes between stops.

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Cabin and technical crew

Victor Williams and Anthony Diaz who work on the Island Hopper plane. Chris Dwyer

Although neither look old enough, Victor Williams has been working the Island Hopper for 34 years and Anthony Diaz a mere 29.

Most crew need at least a quarter century under their belt before they're considered for the much sought-after route, as flight attendants get a two-day break in Honolulu before the return leg -- a rare perk in the world of modern aviation.

Things may soon change, however, so there's a chance that crew may no longer be able to work the entire 16-hour route. Unlike the pilots, they don't rotate.

To say they know the route -- and the passengers -- is an understatement. When they started flying it, aboard a 727, there were just two flight attendants for 70 passengers over seven stops -- one more than today.

As Williams explains: "There was no inflight entertainment. We were the entertainment! The back half of the cabin was 70 passengers, the front half was cargo so there could be anything from pigs to chickens to vegetables. We've watched people grow up. We're the only one to have this type of routing in the whole airline industry. It's definitely a family."

For the sectors from Majuro to Guam, United also has a Field Technical Representative on board -- a specially trained mechanic -- along with a number of spare parts in the event that a technical fix is needed while on the islands.

A plane with 160 people getting stranded overnight on tiny Kosrae is not an option.

There are also complicated computations of both people and cargo at each stop, with both needing to be precisely loaded to maintain weight balance.

Leg 1 Honolulu -- Majuro

The flight leaving Hawaii. Chris Dwyer

By far the longest leg, this five-hour flight takes off from the Reef Runway at Honolulu's Daniel K Inouye International Airport.

But not before dozens of cool boxes and white boxes of mail are loaded. The cool boxes are bringing food -- particularly meat -- for residents of the remote islands where fresh meat is scarce and expensive. The mail boxes are another indication of how the route is a lifeline.

At the gate, posing for a photo, are two airline employees. Based in California, they're heading to tiny Pohnpei for a few days' vacation before then flying on to Guam. They are flight attendants who have always wanted to fly this route.

The flight takes off on Sunday morning but arrives in Majuro on Monday morning because it crosses the International Date Line, taking us forward a whole day.

For the entire flight, there's nothing outside but 50 shades of blue.

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Majuro, The Marshall Islands

The harbor in Majuro, the Marshall Islands. Chris Dwyer

Yokwe! That's the local greeting in the Republic of the Marshall Islands, a country of more than 100 islands and islets. It receives around 5,000 visitors a year -- 1% of the number who visit North Korea -- almost all of whom arrive on the Island Hopper.

As the aircraft starts to descend, a thin ring of atoll emerges suddenly in the distance. It looks barely wide enough to support a road, let alone a runway.

As the brakes are forcefully applied on landing, the waves of the ocean lap gently just meters from the runway. It's a reminder that the country is at enormous risk of rising sea levels, with the average altitude being just seven feet.

Ginny Turner, a British teacher arriving to spend a year in the Marshall Islands. Chris Dwyer

Underneath a sign announcing The Gateway to Micronesia, at the tiny baggage claim where many of those cool boxes reappear, is a woman carrying a British passport.

Ginny Turner explains she's just arrived to work as a teacher volunteering with World Teach for a year. She deliberately chose somewhere far removed -- geographically and culturally -- from her home and the school where she teaches near Ipswich, in eastern England.

There's no chance of getting lost in the Marshall Islands as there's only one road that runs the length of the island. As for shared taxis, they're a bargain at 75 cents per person, regardless of how far you go.

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The Robert Reimers hotel -- one of seven places to stay listed on TripAdvisor -- is a comfortable base with views over the azure waters of the bay, where tuna fishing boats transfer their catch to larger vessels. It's a surprise then that the one thing that's off the menu at the hotel restaurant is tuna.

Wandering the quiet main street, dotted with a number of Chinese-owned supermarkets and stores, the local museum and adjacent church stand out due to their height, as do three young Mormon men in shirt and tie, despite the heat.

Boarding from Majuro for Island Hopper onwards. Chris Dwyer

Inside the museum there's a moving reminder of the plight of many Marshallese, as it chronicles how inhabitants were forced to leave their home islands in the 1940s and '50s when the United States tested dozens of nuclear weapons across the region -- most famously at Bikini Atoll.

A few hundred yards away, next to the island's Post Office, a sign announces the building housing the Nuclear Claims Tribunal.

Leg 2 Majuro - Kwajalein

Back at the airport for the series of flights that eventually reach Guam, the next stop an hour away is the island of Kwajalein, but not before all the passengers are briefed.

It's home to a US Army installation, the Ronald Reagan Ballistic Missile Defense Test Site. That means no photos of any sort are allowed either on approach, while on the ground, or on takeoff. Everyone deplaning -- including dozens of contractors -- also has to remove any headgear before they do so.

On board is one of the rare leisure visitors, a Ukrainian diver joining a number of other specialists to explore some of the region's numerous World War II wrecks. Sites including Prinz Eugen, the escort ship to Germany's legendary Bismarck battleship, have made it a sought-after destination for experienced wreck divers. On landing he'll get on a boat for a 26 hours journey to Bikini Atoll.

On the next takeoff 45 minutes later, the Ukrainian diver's seat is taken by a laid-back electrical contractor from Montana who explains that he works "on missile silos" -- without divulging much more.

Leg 3 Kwajalein - Kosrae

The descent into Kosrae. Chris Dwyer

Next stop is Kosrae, an island of the Federated States of Micronesia which is only visited in three of the four weekly Island Hopper flights. On approach, there are breathtaking and picture-perfect desert islands surrounded by aquamarine waters dotted across the ocean, before suddenly mountains appear on the horizon and a lush green island comes into view, fringed by golden stretches of sand.

The firetruck on standby at Kosrae Airport. Chris Dwyer

The breaks slam on as the aircraft touches the 5,750-foot airstrip -- less than half the length of a runway at Heathrow.

As passengers stretch their legs -- and some aviation fans ask immigration officials if they can get a passport stamp despite not officially entering the country -- it's time to stock up on snacks.

Passengers bemoan the lack of food on board the Island Hopper -- in coach, breakfast is served from Honolulu to Majuro, but then there's only a light snack from Chuuk to Guam around seven hours later. While logistics factors doubtless come into play, it's a complaint heard time and again from passengers -- that and the cost of the ticket, around $2,300 round trip, subject to seat availability and seasonality. (The return leg from Guam to Honolulu can be taken on a 777 as a direct flight).

Kosrae International Airport. Chris Dwyer

It also means that regular fliers stock up with snacks in advance and along the way. In Kosrae, it's fair to say there are pretty slim pickings. Aside from some chips and candy, one table offers a sole spam musubi -- that's rice topped with spam and wrapped in seaweed, sushi-style -- a number of small bananas and local coconut oil in plastic bottles.

Leg 4 Kosrae - Pohnpei

The scenery of Pohnpei island. Chris Dwyer

In common with all the islands en route, beautiful Kosrae is a tempting place to spend a few days. But there's no hanging around. Next up is Pohnpei, one hour behind Kosrae but still part of the Federates States of Micronesia.

Pohnpei from the sky. Chris Dwyer

Once again, after descending over multicolored patches of atoll, a runway appears out of nowhere, while mist-covered mountains have more than a touch of "Jurassic Park" about them. Parts of Pohnpei are some of the wettest on earth, with Mount Nanlaud receiving around 400 inches of rain every year.

Parts of Pohnpei are some of the wettest places on Earth. Chris Dwyer

Pohnpei is also home to the mysterious Nan Madol ruins, called by some the Venice of the Pacific, as it was a city of man-made islands built around channels filled by the oceans, a site that once housed an ancient civilization.

Captain Fitz Fitzgerald, joining passengers on a walk around the departure area, recommends picking up two local specialties from the small stall -- flavored salts and coconut oil.

Back on board, the flight attendant Williams approves of the latter purchase, saying his 84-year-old father swears by it.

Leg 5 Pohnpei - Chuuk

Even splitting up the Island Hopper journey with a night in the Marshall Islands, fatigue definitely sets in after three takeoffs and landings.

The penultimate stop comes at Chuuk, another destination that is world-renowned among divers. That's due to more than 60 wrecks of both aircraft and ships, known as the Ghost Fleet of Truk Lagoon, which serve as a reminder of brutal battles in World War II.

Lifeline: When needed, part of the plane can be curtained off to carry patients to hospital. Chris Dwyer

It's also where another pilot explains the lifeline often played by the Island Hopper. In such remote islands with very limited medical infrastructure, UA154 is often used to transport patients to and from hospitals in Guam.

When needed, there's even a special curtained-off area to allow stretchers to rest across the front row of seats in coach.

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Leg 6 Chuuk - Guam

The view of natural reefs from the Dusit Thani Guam resort. Chris Dwyer

The final flight of the Island Hopper takes us to the US territory of Guam, the largest island in Micronesia and home to around 160,000 people.

All of a sudden, blue swimming pools and neat white houses, a green canopy of forests, highways and golf courses appear below.

Local Guam dishes. Chris Dwyer

"Hafa Adai!" is the oft-heard welcome to an island that boasts incredible reefs, rolling green mountains, countless beaches, intriguing local dishes and fascinating history.

Those reefs allow guests at the Dusit Thani Guam to walk out from the beach and snorkel safely in just a few feet of water, seeing a remarkable diversity of marine life close to shore.

A local Guam speciality of fresh coconut and wasabi, served sashimi style. Courtesy Chris Dwyer

Indigenous Chamorro culture on Guam then provides fascinating historical insights, including the unusual but ingenious latte houses. Stones known as "latte" used to act as the base of these one-story houses, the oldest of which date back to around 800 CE, while they are still found dotted across the island.

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Elsewhere, activities include a boat tour on the Talofofo river where a Japanese soldier Yokoi spent an incredible 28 years in hiding after the end of World War II, holding out in the underground cave he had dug until 1972. Today a museum is on the site by his hideout.

Some of Guam's "latte" stones date back more than 1,200 years. Chris Dwyer

Then there are local dishes not to be missed such as the ingenious coconut wasabi, where the flesh of a very ripe coconut is sliced, sashimi style, before being served with soy sauce and wasabi. It's much better than it may sound. Kelaguen is another uniquely Guamanian dish where fish, beef, or chicken is marinaded in lemon juice, coconut and chili. The country is also rightly very proud of its own tradition of barbecue.

Ultimately there are many direct flights to Guam from around Asia, but in common with the other destinations it visits, the Island Hopper from Honolulu feels a special way to arrive there, a throwback to a gentler and very different era of aviation.