Editing Unit load device (section)

==Main-deck ULDs==

On the main deck of cargo planes are {{convert|79|to|108|in|mm|0}} tall ULDs with footprints similar to those of {{convert|88|in|mm|0}} or {{convert|96|in|mm|0}} wide pallets and {{convert|62|in|mm|0}} or {{convert|125|in|mm|0}} long. A {{convert|62|in|mm|0|adj=on}} wide × {{convert|88|in|mm|0|adj=on}} tall ULD is half the volume of a {{convert|125|in|mm|0|adj=on}} × 88 inch pallet. The 20 foot pallet is {{convert|238|in|mm|0}} long and {{convert|96|in|mm|0}} wide. What the actual dimensions of contoured upper deck ULDs are is very hard to know, because most manufacturers only profile width, length and height data.

There are several common types of contoured main deck ULDs, that are contoured (curved to fit in the plane's body) to provide as much cargo volume as possible. Initially ULD contouring was simply a triangle removed from one or two corners of the profile of the ULD, such as the common LD3 and LD6. Main deck ULDs use curves for the contoured shape to truly maximize cargo volume. Upper deck ULDs are just like lower deck ULDs that are either the full width of the plane with two corners of the profile removed (lower deck LD6 lower), or that container is cut in half, down the center line of the plane, (lower deck LD3 and upper deck AAX).

Main deck ULDs and pallets are not only taller than lower deck ULDs, they are frequently two or four times longer. They are usually organized like an LD6, using the width of the plane and missing two profile corners, or two very long LD3s, stored in parallel to use the plane's width and each missing one profile corner, but often twice or four times as long from plane's nose to tail.

Many air cargo companies use main deck ULDs that have both features called dual-profile, so that on smaller planes such as the Boeing 727, they are stored widthwise and have two corners contoured, and on the bigger Boeing 767, they can be rotated 90 degrees and shipped in parallel like LD3s, so that only one corner is contoured when being used like an LD3. This greatly simplifies transportation of cargo containers at slight cost of cargo volume.