Desperate for more planes, cargo airlines are buying up aging passenger jets. Here's how they're converted to fly Amazon packages instead of people.

• Cargo carriers and e-commerce giants are buying up aging airliners and turning them into cargo jets.
• Israel Aerospace Industries is one conversion firm that the likes of Amazon have entrusted with their planes.
• The process can take up to around 120 days, and slots are booked years in advance.

A unique fleet of aircraft is fueling the explosive growth of e-commerce as consumers turn to online shopping during the pandemic and retailers promise faster-than-ever delivery times.

And while air travel remains signifcantly lower due to COVID-19, some former passenger aircraft are avoiding early retirement by finding a second life moving cargo. Logistics giants, meanwhile, are using the airline industry's downturn to grow their fleets by acquiring aging passenger aircraft for a fraction of what they'd sell for new.

Amazon, for example, bought 11 Boeing 767-300ER passenger aircraft from Delta Air Lines and Canada's WestJet in January for cargo conversion. While the pandemic had rendered the planes obsolete for flying passengers, they're now prime candidates to fly packages instead.

But converting a passenger plane into a cargo carrier isn't as easy as just taking out the seats. The aircraft also needs to be extensively retrofitted to handle the inanimate payload. It's months-long process currently can only be done by a handful of firms around the world, and the conversion can often cost as much as the planes themselves.

Luckily, business is booming.

Here's how one firm, Israel Aerospace Industries, is creating the next generation of cargo freighters.

Israel Aerospace Industries has been converting passenger jets to freighters for four decades now, starting with the iconic Boeing 747.

A Boeing 747-400BDSF cargo plane.      InsectWorld/Shutterstock.com

Over the years, the firm has grown to become the go-to for converting some of Boeing's most-popular aircraft including the 737 Classic, and the 767-200.

A Boeing 737-200 freighter.      Thiago B Trevisan/Shutterstock.com

But the main focus for newer customers like Amazon are the Boeing 737 Next Generation and the Boeing 767-300ER.

Converting a Boeing 737-800 to a cargo plane.      Israel Aerospace Industries

It starts with an airplane. The customer first sends the aircraft details, including the serial number and information about the onboard systems to the firm, where a new design is crafted.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

And upon arrival, the entire interior is stripped so that engineers can rebuild with a clean slate.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

"Actually we are opening the aircraft," Yossi Melamed, general manager of the Aviation Group of Israel Aerospace Industries, told Insider, "taking everything out."

Converting a Boeing 767-300ER to a cargo plane.      RONEN ZVULUN/Reuters

Passengers seats, for example, are no longer needed on these planes and are removed.

Converting a Boeing 767-300ER to a cargo plane.      Amir Cohen/Reuters

The cabin floor is then removed and replaced with a reinforced structure that allows the aircraft to handle the weight of the cargo pallets, and allows for easier loading as rollers help guide and move the pallets.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Another key differentiator between a cargo plane and a passenger plane is the cargo door, located on the side of the fuselage. Engineers start by cutting out a section of the fuselage.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Then a "plug" is installed in its place.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

And the cargo door is installed.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

The aircraft has to be held in place while the fuselage modifications are made to ensure it doesn't twist.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Without the door, the aircraft would be limited to carrying only small packages and pallets.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Engineers then go to work on the aircraft's systems.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Some cargo carriers are opting to install a modern cockpit for the Boeing 767, for example.

Converting a Boeing 767-300ER to a cargo plane.      RONEN ZVULUN/Reuters

Windows are also covered as there are no passengers.

Converting a Boeing 767-300ER to a cargo plane.      RONEN ZVULUN/Reuters

And a rigid barrier is installed to protect the cockpit from the cargo in the back.

Converting a Boeing 767-300ER to a cargo plane.      Amir Cohen/Reuters

Once all the modifications are complete, the aircraft is cleaned and washed while paperwork is completed behind the scenes.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

The newly-converted aircraft then takes flight to test its airworthiness in the new configuration, followed by delivery to the customer.

Converting a Boeing 737-800 to a cargo plane.      Israel Aerospace Industries

Some newly-converted freighters will have a trace of their former life. This aircraft once flew for American Airlines, for example.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

The conversion process takes, on average, around 100 days. But if a customer chooses to have the firm handling extra work like maintenance and painting, it can take as long as 120 days.

Converting a Boeing 767-300ER to a cargo plane.      RONEN ZVULUN/Reuters

Israel Aerospace Industries has completed over 700 of these conversions on a wide range of aircraft from business jets to passenger jets.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Melamed estimates that between 60%-70% of Amazon's Prime Air fleet is comprised of aircraft converted by his firm. "I want to believe that Amazon is trusting us and we are trusting them," Melamed said.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Aircraft are converted at three of the firm's sites around the world in Israel, Mexico, and China. Another location is slated to open this year, though the location remains a secret. The company plans to have seven sites by 2024.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Melamed is confident that the demand for freighters will only grow in the next few years as commercial passenger flights, which also carry cargo, took a big hit during the pandemic.

Converting a Boeing 767-300ER to a cargo plane.      RONEN ZVULUN/Reuters

"[Freighters] kept the world moving when all the commercial passenger business was down," Melamed said.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

But even once the pandemic ends and traffic returns to 2019 levels, Melamed believes that freighters will continue to be in demand as the amount of freight that needs to be transported across the globe increases.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

Israel Aerospace Industries is also leading the charge on a new freighter plane, the cargo variant of the Boeing 777-300ER, nicknamed the "big twin." It will be the largest twin-engine Boeing cargo plane when it flies.

Converting a Boeing 777-300ER to a cargo plane.      Israel Aerospace Industries

"I would say that it's the best candidate to be converted after the 747," Melamed said.

Converting a Boeing 777-300ER to a cargo plane.      Israel Aerospace Industries

Read More: Boeing just announced the definitive end of the legendary 747 as cargo giant Atlas Air places an order for the final 4 planes

So why don't airlines just buy new aircraft? It comes down to how cargo airlines utilize their freighters.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

A new aircraft flying for Delta Air Lines or American Airlines might be flying all the time while a Boeing 767 for Amazon might rest longer in between flights, also known as having a low utilization rate.

A Delta Air Lines Boeing 767.      Nicolas Economou/NurPhoto/Getty

It makes more economic sense to spend less on aircraft with low utilization rates, just like a commuter wouldn't want to have a Mercedes as a station car.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries

And of course, boxes don't care if they're flying in a new Boeing 767 or a 30-year-old Boeing 767.

Converting a Boeing 767-300ER to a cargo plane.      RONEN ZVULUN/Reuters

A 767 conversion can cost as much as $13-$14 million, according to Chris Seymour, head of market analysis for Cirium. That's around as much as a used 20-year Boeing 767 in "superb" condition might cost.

An Amazon Prime Air Express Boeing 767-300F cargo plane.      Stephen Brashear/Getty Images

Read More: The airline industry's loss is Amazon's gain as the e-commerce giant purchases 11 Boeing 767 airliners to use as cargo planes

And of course, there's the maintenance issues associated with purchasing an older aircraft.

Converting a Boeing 767-300ER to a cargo plane.      AMIR COHEN/Reuters

But even if a company spends $30 million in total on acquisition, conversion, and maintenance costs, it's still cheaper than paying the current list cost price of $220.3 million for a new Boeing 767-300F.

A FedEx Express Boeing 767-300F cargo plane.      Sundry Photography/Shutterstock.com

Source: Boeing

Demand is currently sky high. While the process only takes a few months, new 767 conversion customers may have to wait almost two years as Israeli Aerospace Industries is fully booked through 2022.

Converting a passenger aircraft to a cargo plane.      Israel Aerospace Industries

"If somebody will insist that he wants a slot [for 2022], I would say go to the Western Wall, put in a piece of paper, and ask God for a slot," Melamed said.

Converting a Boeing 767-300ER to a cargo plane.      Israel Aerospace Industries