Hey there, if you’re here, chances are you’re either a fleet manager, a cargo handler, or someone who’s been pulling their hair out trying to keep ULDs (Unit Load Devices) in good shape between flights. As a ULD supplier, we see way too many guys cut corners on storage only to end up with dented containers, bent pallets, or parts that are broken before they even hit the tarmac. That’s money down the drain—especially when replacing a single LD3 container can cost you a small fortune, and downtime means lost cargo space, missed flights, and frustrated shippers. Today, I’m breaking down exactly how we teach our customers to store ULDs long-term and short-term, no fancy jargon, just real stuff we’ve learned from working with airlines and cargo operators for years. ULD
First off, let’s get one thing straight: ULDs aren’t just metal boxes or pallets you can throw in a corner. They’re engineered to hold hundreds (sometimes thousands) of pounds of cargo, built to withstand extreme temperatures, rapid loading, and the constant vibration of flight. Skimp on storage, and you’re weakening their structural integrity over time. We’ve had a customer send a ULD back after three months of sitting outside, and the entire frame had rusted so bad it failed its next inspection. Don’t be that person.
Let’s start with short-term storage—this is the stuff you do if a ULD isn’t going to be used for less than a month, just sitting at the gate, tarmac, or a temporary yard. First rule here: keep it off the ground. I see so many folks just leave ULDs sitting right on the asphalt, and that’s a mistake. Asphalt gets hot, it holds moisture, and over time, it can warp the bottom corners of the container or leave rust marks that eat away at the metal. Grab some wooden pallets or rubber mats (we stock these as add-ons for exactly this) and set the ULD on top, lifted at least 6 inches off the ground. For pallets, make sure the ground is level too—no one wants a 40-foot container tilting, that’s a tripping hazard and can stress the frame.
Next, protect the interior and exterior from the elements. Even a few days of rain or intense sun can cause problems. If your ULD has a hard shell (like a container), close and latch all the doors tightly. We always suggest tossing a cheap, breathable cover over the top to block UV rays—sunlight breaks down the paint and seals, making the metal more prone to rust. For open pallets or net ULDs, drape a weather-resistant tarp over the top, but leave the edges loose so air can circulate. Trapping moisture under a tarp is a worse problem than the occasional light rain, trust me. And whatever you do, don’t leave loose cargo inside the ULD when storing short-term. Even small things like straps, buckets, or leftover packaging can shift, scratch the interior, or get blown away and lost.
Now, long-term storage—this is the big one, for ULDs that won’t be used for a month or more. This is where we see most of the mistakes, so pay attention. First, pick the right location. Ideal is a covered, climate-controlled warehouse, but we know not every operator has space for that. If you have to store outside, find a spot that’s well-drained (no puddles forming after rain), shaded as much as possible (we use a combination of overhead awnings and natural tree cover where we can), and away from chemical spills or heavy machinery that could bump into the ULD. One of our clients stores all their retired ULDs in an old hanger they converted, and it’s cut their repair costs by 40% in two years—proof that spending a little on good storage saves cash long-term.
Before you even put the ULD into long-term storage, do a quick pre-storage check. We tell our customers to go through this every single time: wipe down the entire ULD with a mild detergent and water to get rid of dirt, oil, or salt residue (salt is super corrosive, especially if you’re operating near coastal airports). Inspect all the moving parts—latches, hinges, wheels, locking pins, the whole works. Lubricate any metal parts with a light, corrosion-resistant oil (we recommend a silicone-based lube for hinges, not heavy grease, that just picks up dirt). Tighten any loose bolts—vibration from flights can shake things, and over time that can lead to cracks. If you spot a small dent or a scratch, don’t ignore it—sand it down, touch up with primer, so rust doesn’t set in. A $5 can of primer beats a $500 repair later, hands down.
Once the ULD is prepped, get it elevated properly for long-term storage. We use heavy-duty concrete blocks or custom ULD jack stands (we sell these too, they’re worth every penny) to lift the entire frame 12 to 18 inches off the ground. This prevents ground moisture from wicking up into the metal, and makes it way easier to inspect the bottom later without crawling on dirt or wet grass. Never stack ULDs directly on top of each other for long-term storage—this puts unnecessary stress on the lower ULD’s frame, and if you forget how many are stacked, you’ll scratch up the top of the lower one. If you have to stack, use custom wooden spacers between each ULD, and limit stacks to no more than 3 total for small LD containers, max 2 for 40-foot ones.
Now, for maintenance while in long-term storage. Don’t just tuck it away and forget about it—check on your stored ULDs every 30 to 45 days. Open the doors, wipe down any new dust or moisture, check the lubrication on moving parts, and make sure there’s no standing water inside or under the ULD. If you’re storing in a humid area, we suggest placing a few silica gel packs inside the container (leave them in a mesh bag so they don’t get lost with cargo) to absorb excess moisture. For ULDs with wheels, if they’re going to be sitting for months, rotate the wheels every once in a while to prevent flat spots in the rubber—flat wheels are a quick fail when you need to move the ULD again.
Wait, let’s talk about specific ULD types too, because storage isn’t one-size-fits-all. For example, a Type A container (the big, side-opening ones) is way bigger and heavier than an LD3, so their storage needs are different. We always advise Type A ULDs to be stored on their side if possible when not in use—this takes weight off the top and bottom edges, which are prone to bending if left upright for too long. Net ULDs (the open ones with the metal frame and nylon net) need extra care with the net—make sure it’s not stretched or hanging loose when storing, and if possible, remove it and store it in a dry, flat place separately, so it doesn’t get snagged or stretched out. For ULDs with refrigeration units (we call these reefer ULDs), you have to disconnect the battery, drain all water lines, and leave the unit’s door open a crack to prevent mold buildup inside the cooling system—skip that, and you’ll have a $1,000 repair for a clogged evaporator.
I can’t tell you how many times we’ve heard horror stories from customers who ignored these tips. Last year, a regional airline stored 10 LD3s outside for 6 months, no prep, no cover. When they pulled them out for peak cargo season, 7 of them failed their inspection because of rusted frames and bent corner castings. They had to buy new ones at a premium, and lost out on a $200k cargo contract because they didn’t have enough ULDs available. That’s the kind of stuff that makes us want to sit down with every operator and walk through storage basics—because it’s that impactful.
Now, let’s wrap this up with some quick, no-nonsense do’s and don’ts to keep you from making the same mistakes:
DO:
- Elevate all ULDs off the ground, regardless of storage length
- Do a pre-storage inspection and clean every time you put a ULD away
- Check stored ULDs every 30 days for moisture, rust, or loose parts
- Use covers or a covered space to block UV and rain
- Lubricate moving parts before long-term storage
DON’T:
- Leave ULDs sitting directly on asphalt or concrete
- Stack ULDs without spacers for more than a few days
- Skip cleaning or rust prep before long-term storage
- Leave batteries in reefer ULDs while stored long-term
- Trapping moisture under tarps or inside closed containers
Dolly If you’re someone who’s tired of dealing with ULD damage or need to upgrade your storage setup for your fleet, we’re here to help. As a ULD supplier, we don’t just sell containers and pallets—we help you keep them in good shape, because that means better service for your customers and less hassle for you. Whether you need new ULDs, storage accessories like jack stands or covers, or just a chat about how to optimize your current storage, reach out to our team to get started. We work with small cargo ops and big airlines, so no matter how many ULDs you have, we’ve got your back.
References
- International Air Transport Association (IATA) ULD Maintenance Manual, 2022
- Federal Aviation Administration (FAA) Guidelines for Aviation Cargo Equipment Storage, 2021
- Air Transport Association (ATA) Specification 100: Unit Load Devices, 2020
Wuxi Aviation Ground Equipment Co., Ltd.
Wuxi Aviation Ground Equipment Co., Ltd. is well-known as one of the leading uld manufacturers and suppliers in China. Please rest assured to buy or wholesale discount uld for sale here from our factory. For price consultation, contact us.
Address: No.18 Dingxiang East Road, Hudai Town, Binhu District, Wuxi, Jiangsu, P.R. China
E-mail: sales@wxagecl.com
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