How Does Freight Travel on an Airplane?

Goods travel globally every day, either by air, sea or ground.  The fastest method of transportation, of course, is by air.  It’s common to see semi-trucks on the road, carrying their load inside its trailer.  On a ship, large cargo containers are stacked on the decks and inside the cargo holds.  So how does freight travel on an airplane?

Unit Load Device

Freight that is to be shipped via airplane is packed either onto a pallet or inside a container.  Known as a unit load device (ULD), these two types of ULDs not only protect goods while in transit, they also provide for more efficient loading and unloading of the cargo.Cargo being loaded onto an airplane via K loader 

ULDs are designed to keep goods secure throughout the flight – from take-off to landing, and especially during turbulence.  They prevent the cargo from sliding or shifting and potentially damaging the aircraft.  More importantly, ULDs keep the cargo in the designated location in the hold, as movement could affect the aircraft’s weight and balance, negatively impacting control of the aircraft.

First introduced in the late 1950s, there were many different sizes and shapes of ULDs created for the various types of airplanes.  Manufacturers soon began to standardize ULDs for each aircraft according to their individual specifications. 

Due to the high number of safety incidents, damage and loss caused by ULDs, the International Air Transport Association (IATA) formalized the use of ULDs in 2013.  IATA developed an all-inclusive reference manual (ULDR) that outlines regulatory and aircraft requirements for ULDs as well as industry standards and procedures for manufacturing, repair, maintenance and handling of ULDs.

Today, there are many different types and sizes of ULDs, each designed specifically to fit inside the cargo hold of a particular type of aircraft.  There are also specialized varieties of ULDs used to hold specific cargo.  This includes the Temperature-Controlled Container (TCC), Fire Resistant Container (FRC), Fire Containment Cover (FCC), and even ULDs that have been modified to carry animals.

ULD Pallets

An air freight pallet is one of the two types of ULDs.  It is a large, durable, flat base made of aluminum.  Resembling a large cookie sheet, the edges of the pallet have rims which secure a cargo net used to restrain the freight.  Prior to palletizing and netting, the cargo is stacked according to specific dimensions and weight.

 The three most commonly used air freight pallet types are PMC, PAG and PQA.  The PMC pallet is the largest of the three and measures 96 x 125 x 1.1 inches.  Its maximum gross weight is 15,000 lbs. 

The PAG pallet comes in second according to size, measuring 88 x 125 x 1.1 inches and carrying a maximum gross weight of 13,300 lbs. 

The smallest of these three freight pallets is the PQA at 60.4 x 96 x 1.66 inches.  Its maximum gross weight is 5,400 lbs.       

ULD Containers

A container is the other type of ULD.  Also made of aluminum, a ULD container is comparable to a hollow cannister that holds cargo.  Unlike standard box trailers found on trains, ULD containers are designed with unique and somewhat odd-looking angled sides.  The precise dimensions causing these angled sides allow the containers to fit perfectly in a standard airplane, thus maximizing the allotted space.

There are different types of ULD containers that can fit several aircraft types.  The most common are:

LD3 – the most common ULD container.  It can be used on all Airbus widebody aircraft, as well as Boeing 747, 777, and 787 airplanes.  It can also be used on smaller aircraft such as the ATR 42 and ATR 72.

LD1 – wider than the LD3 but with the same height and depth.  The LD1 is also designed for use on a Boeing 747; ho

wever, it is not commonly available.

LD2 – made to fit the narrow fuselage of the Boeing 767.  An LD3 would also fit, but it would be inefficient as it takes up the same space as two LD2 containers.

LD7 – a double-width container (compared to the LD3) used on a Boeing 777 and Boeing 787.

LD3-45 – designed to fit the Airbus A320 family aircraft.  They are standard LD3 containers but lower in height in order to fit the narrow-body of the A320.

Loading Freight Onto The Plane

Goods to be transported by airplane arrive at the airfield via truck.  With the help of a fork lift, the ground crew unloads the cargo from the truck and positions it onto an air freight pallet or into a ULD container.  In order to lift the freight to the height of the airplane’s cargo door, ULDs are placed on a main deck loader, or “K loader”. 

The K loader has two platforms which raise and descend independently.  The loading platform is where the ground crew places the ULDs to be shipped.  The front platform, known as the bridge, contains the operator panel and literally acts as bridge between the loading platform and the plane’s cargo compartment. 

Once the ULDs are secure on the loading platform, the operator raises it to the same height as the bridge, which is also the same height as the aircraft door.  Both platforms are fitted with automated rollers that are controlled by the operator.  The rollers move the ULDs from the loading platform to the bridge and onto the plane.  ULDs are then repositioned by a separate set of rollers contained inside the plane.

Air Freight Specialists

Grand Aire has been a leading air service provider for over 35 years.  Our Logistics Specialists are accessible 24/7/365 to provide you with the best air transportation options available.  Simply call 1-800-74-GRAND or email our team at