Global air cargo operators, whose business models are largely built on delivering the lowest costs, are relying on the inherent savings and efficiencies that come from converting retired aircraft into hard-working "cargo dogs."

In an age fueled by the explosion of global e-commerce, with the click of a finger you can order a bouquet of roses, delivered via a shipping container filled with rose bushes, shipped and placed on your doorstep the next morning.This on-demand delivery capability is due in large part to the world’s rapidly growing fleet of air cargo aircraft.The fleet is becoming more and more numerous.

In fact, according to a Boeing report, the air cargo industry will grow at a rate of 4.2% over the next 20 years.

In terms of the number of new aircraft, Boeing reported that by 2035, China will need 930 new freighters and 1,440 modified freighters to meet market demand.

This means that the number of global cargo aircraft has increased by nearly 70%.

(Boeing forecasts, at least for China in the past nearly 20 years, are usually quite accurate, so for the future development of civil aviation forecasts, Boeing's forecast conclusions are usually among the best!) The forecast divides freighters into 550 new large production freighters, 380 new medium wide-body freighters, 400 wide-body converted freighters and 1,040 medium converted freighters. Interestingly, Boeing's forecast makes no mention of the smaller regional jets needed to fill very short-haul regional routes. Probably because they don't make that type of product anymore.) But no matter how you classify it, 1,440 of any airframe combination is a lot of passenger-to-cargo (P2F) aircraft, meaning that segment of the market is looking pretty good right now. "The conversion market is very good at the moment and all our routes for the rest of the year are full," said Mike Andrews, program director for passenger conversion at PEMCO World Air Services. "We have been in the passenger-to-cargo business for more than 20 years and have completed more than 350. At the moment we have only converted 737-300 and -400 aircraft out of a total of 130 we have converted so far." "We're probably covering 60 to 70 percent of small narrow-body modifications today," he said. "The 737 is a very good 'regional' freighter. The Type 300 and 400 will carry about 43,000 pounds and 46,000 pounds of cargo, respectively, and both models will have a range of approximately 2,500 nautical miles.

Pemco World Aviation Services Company (Pemco) delivered its first B737-300 passenger-converted freighter aircraft to China's Longhao Aviation Group. It has nine pallet positions, up to 43,100 pounds of payload, 4,600 cubic feet of total volume, and a maximum range of over 2,000 miles.Gary Warner, president of Precision Aircraft Solutions, said his company is also currently experiencing an ""upward"" market. Like PEMCO, Precision Aircraft Solutions only performs P2F modifications on one airframe type – in their case, the Boeing 757-200 series.Warner also said much of the increase in global refit rates may be related to the growth of e-commerce and the need for fast delivery from e-retailers' customers.“ATSG and Atlas have been buying and retrofitting 767s to meet the needs of e-commerce giant Amazon,” he said. “In the narrow-body segment, China is seeing phenomenal growth in demand for freighters.Chinese e-commerce giants Alibaba and JD.com are currently driving demand for volume freighters like the 757. ""
""So far, we have modified more than 80 B757-200PCF (precision modified freighters),"" he said.
""The 757-200PCF has matured and remains in high demand around the world. As a heavy-lift transport aircraft, it bridges the gap between the largest narrow-body transports and the smallest wide-body transports.""
Of course, just like the overall development of the aviation industry, although the current P2F business is experiencing a bright future, there is also a dark cloud hiding behind it - that is, the supply of high-quality, low-altitude flights is decreasing.
P2F modding: only for the best needs.
""When it comes to modifications, we look for airframes that have relatively fewer cycles than normal,"" Andrews said.
""The 'life' of the 737 is about 70,000 operations, and we hope to be at the sweet spot of about 35,000 operations. This is a good life stage for the aircraft as a cargo aircraft.""
As for the 757-200, Warner said the typical aircraft with optional modifications is 15 years old and has flown less than 30,000 times. This would typically give the 757-200PCF an additional 15 years of service life before the aircraft reaches its effective limit of hours or cycles (LOV).
Regardless of the type of aircraft, the number is decreasing every day and the aircraft are getting older.
""Operators of older aircraft, such as legacy 727s, early 737s and 757 variants, are realizing that the ideal window of opportunity to retrofit the 737-300, -400 and 757-200 is closing,"" Warner said.
""If you do not choose to take advantage of the opportunities available today, you may be forced to use older aircraft until the next generation of freighters such as the A320/321 becomes available.""
""Of course, there's a sweet spot for everything,"" Andrews said. ""While waiting for the new 737 MAX, airlines are still actively using the 737-300 and -400, but when those airframes come off the line, they will be ready for retrofitting. This is good for our business.""
However, as e-commerce expands rapidly around the world, sooner or later air cargo operations will need to transition to the next generation of retrofitted freighters. All P2F modification companies are already preparing for this day.
""We expect demand for the 757-200 to decline over the next five to seven years, replaced by next-generation narrow-body freighters such as the A321,"" he said.
So now is the time for P2F conversion suppliers to start looking at which airframes they will bring to market.

“We talk to customers, evaluate aircraft types and understand the typical operating costs for a specific aircraft type, including all maintenance costs,” Warner said. ""The biggest difference now is that we are also paying attention to the materials used by OEMs in the airframe, the structural design concepts of each aircraft, and the individual subsystems.""

Last year,PEMCO delivered a 737-400 Combi aircraft to First Air, an airline in the Canadian Arctic and remote regions (photo :PEMCO); (Right) A newly completed 757-200PCF awaits delivery. ""These new models have more integrated systems than the older models. I'm not talking about fly-by-wire, I'm talking about the various computer systems that are on these aircraft.""

""There will definitely be a transition for passenger-to-cargo project from the structural/maintenance aspect to the current structural/maintenance/system modification.""
The right plane is just the beginning. Once upon a time, a typical P2F refit was little more than ripping the interior apart, painting the Windows, cutting a hole in the fuselage, and fitting in a cargo door. Today is different. These are highly complex aircraft that, for U.S. airlines, require an FAA Supplemental Type Certificate (STC). Warner explained that based on Precision Aircraft Solutions' experience, it takes about 36 months from start to finish all the engineering, equip the first aircraft and get approval. But it all starts with figuring out how to incorporate a modification project into a specific aircraft model. ""There are two ways to get the engineering information you need,"" he said. ""One is to use OEM data under contract, and the other is to reverse engineer it on the actual aircraft. Both are legal, but clearly very different approaches.""



We chose the reverse engineering approach. So first we need a verification plane." Warner said. "We also have a contract with one of our MRO 'partners' to do this work. It is important that they have a hangar where they can service the aircraft for modification. It will spend approximately two years on the ground completing all survey, design, installation and STC approvals.

One of the first tasks of Precision's B757-200PCF main cargo door installation is to remove and replace the lower door frame and precision manufacture your own main cargo door.
""Once the aircraft is in the hangar of the MRO, the first step is to remove the cabin interior equipment and then investigate and measure the interior space,"" he said.
""We are also performing the same steps on other aircraft to develop a better level of geometry for this aircraft.""
""We used this as a basis for the retrofit structural design, and then further delve into the external airframe load factors,"" Warner added.
""We then used this data to develop finite element models of the aircraft and design concepts for changes to the system."" It's all about de-risking the project.""
Warner explained that in addition to all the work involved in preparing the first aircraft for the P2F-modified STC, the owners of the aircraft will, in all likelihood, be subject to rigorous inspection by the MRO.
Therefore, when the aircraft is redelivered at the end of the STC/ modification process, it is necessary to conclude all work, sign the log book, and release the aircraft for normal use when all work is completed.
""We have also developed a maintenance schedule for the aircraft with lower maintenance times, which will allow operators to make more use of the operational time of the airframe,"" he said.
""It takes into account the difference between an aircraft operating as an airliner and one now operating as a less utilized cargo company.""
Once the STC and other appropriate international approvals are obtained (depending on where the aircraft will be operated), PEMCO and Precision aircraft Solutions need approximately 90 days to complete a typical refit.
Andrews said: ""This includes installing our proprietary hydraulic cargo door, reinforcing the floor structure where needed, and installing a cargo loading system.
""We've got all the hardware and materials we need, it's a very simple process.""
The conversion rate of P2VIP is also on the rise.
While passenger-to-freighter conversions account for the largest market share by far, there is also a growing trend to convert commercial aircraft into high-end business jets and VIP jets.
Flying Colors has become a leader in this space, working their magic to transform ""retired"" Bombardier (Canada) regional jets (CRJs) into what they advertise as the CRJ ExecLiner modified family of aircraft.
Sean Gillespie, Executive Vice President of Flying Colours, said: ""The market for high-end business aircraft conversion projects is still active. ""From our perspective, the most popular modified aircraft we've seen so far is the Bombardier CRJ200. We have also worked on the CRJ700 and the 900, but the 200 is the most popular."" While the CRJ series is currently the company's most popular model, Gillespie said other models, including the Embraer 135 and Donnier 328, are prime candidates for the company's refit program. And, just like the P2F modding market, Gillespie said Asia is currently the most active region for P2VIP modding.
""We have recently delivered two execliner aircraft to ResortsWorld of Malaysia and we have also done a CRJ200 conversion project for Sparkle Roll, a Chinese company,"" he said.
""When these eight aircraft are converted, they will represent a mix of regular passenger aircraft and executive VIP business aircraft."" ""Right now, we're also seeing increased demand in North America, which in part reflects current sales conditions,"" Gillespie said.
""Execliners that are reconfigured often meet the needs of owners with lower budgets and shorter delivery times.""
Gillespie says every ExecLiner starts with an inspection of the aircraft, just like any executive completes a mission. ""The key factor for us when considering the conversion of an airliner is the number of hours the aircraft flies,"" he explained.
""A CRJ with short engine time, short flight time and well-maintained aircraft can really be a good alternative to used business jets.""
""We set maintenance schedules to manage any necessary upgrades or overhauls to the airframe and systems. We also designed the engineering process for the internal renovation to meet the needs of the owners."" ""Gillespie said."

A CRJ200 retrofitted for VIP mode



"Then we go through the installation, completion and delivery process on the aircraft," he added.
"The whole process could take anywhere from four to 10 months, depending on the overall condition of the aircraft, the internal complexity and any modifications we have to make."
While ExecLiner's ""standard"" cabins are high-end, Gillespie says their customers have made some pretty exotic requests.
"We had a client who really liked the rotating bed, which required some unique engineering," he says.
"Even in a fairly standard interior, design engineering can be challenging, but that's what we do."" We have years of experience in solving these unique challenges."




Converting passenger planes into freighters is big and lucrative business.
Although you may not have heard much about it, converting passenger planes into freighters is big business.
Boeing expects demand for 2,600 new or modified freighters to be worth more than $300 billion over the next 20 years.
About two-thirds of that will be aircraft modifications.
These modifications are a core business for Boeing, which controls about 90 percent of the freighter market.
Please note that each aircraft and each aircraft type is unique and I try to keep it simple and clear, but any modification is complicated and can take months.
In aircraft modification, there are some basic steps that are fairly common.
1. Prepare
When an airliner enters a factory ready to be converted into a freighter, part of the cabin is stripped and the previous owner's logo is removed.For any modifications to the fuselage, the aircraft can be jacked up to a neutral stress point.This takes about 4 weeks.
2. Block the Windows
Next, plug the passenger Windows.On cargo planes, passenger Windows are not only pointless, but removing them saves money on maintenance and improves safety.Blocking Windows reduces maintenance and increases safety
3. Remove cabin equipment
The kitchen, the seats, the overhead lockers, the bar on the plane - none of these things were needed on a cargo plane, so they were removed
4. A new door needs to be installed
Usually, a cargo door large enough is installed at the front of the fuselage.This is slightly more complicated than removing the seat and is done in stages.First, a new upper frame housing section is to be installed and riveted to the fuselage.Then remove the lower frame housing section.A new lower frame housing was installed into the prepared cut-out location, replacing the old lower frame housing, and fixed to the fuselage.The cuts in the front and tail of the frame were replaced with new, reinforced frames.Then install the door and its structure.
5. Install new, high-strength cabin floors
When that was done, attention returned to the cabin, now an empty space.The cabin floor was replaced by a higher strength floor, equipped with the necessary conditions for cargo loading movement such as ball pads and roller tracks.To carry as much cargo as possible, the floor area needs to be maximized.The cabin floor also needs to be strong enough to withstand the load.

The cabin was cleaned out and the old cabin floor was replaced with a high-strength floor suitable for cargo pallets

6, the final check test, after the completion of you can start to use
Finally, everything needs to be checked.There is a schedule of tests that need to be executed.Inspect the aircraft, conduct test flights, and prepare documentation.

7, a simple way to extend the service life of the aircraft
As Jay Singh pointed out in his book Simple Flying last year, converting passenger aircraft into freighters is an effective way for airlines to extend the life of their aircraft and generate further revenue.
Although complex, it is cheaper to retrofit existing aircraft than to buy new ones.
When airlines have new aircraft added to their fleets, they usually select the oldest aircraft to retrofit.
For this reason, we can still see some classic models like the Boeing 727 at airports, and can expect to see Boeing 747s - carrying only pallets of cargo rather than passengers - in the coming years.