(Bloomberg) -- With every passing day it’s getting more likely that thousands of 40-foot boxes on board the ship blocking the Suez Canal may have to be hauled off.

The Ever Given, a 400-meter long container ship with almost $1 billion of cargo on board, jammed itself fast into the banks of the waterway on Tuesday, and estimates for it to be freed have now risen to over a week. Tugboats have so far failed to shift the behemoth and some of the smartest minds in the salvage world are hoping dredging will allow them to move the freighter. It might just take a while.

But time is a luxury the ships using the Suez Canal don’t have. The blockage is holding up something like 10% of global trade and a swath of imports that are critical to Europe’s supply chains and industry. Scores of ships have already decided to go the long way around -- passing the southern tip of Africa -- also depriving Egypt of vital revenue. So there’s pressure to get the ship floated and out of the way as soon as possible.

If the dredging isn’t working, or if it’s too slow, then one of the first things the ship’s salvors will do to float the boat is to remove its fuel and ballast so that it sits higher in the water.

Precedents

But the longer the saga rolls on, the more pressure will mount to remove cargo. And history shows that lightening the Ever Given might ultimately be what frees it.

Back in November 2004, another vessel, this time a Suezmax-class oil tanker named Tropic Brillance, ran aground after mechanical problems in the canal, wedging itself across the conduit in a similar way to the Ever Given. Canal authorities were forced to close the canal. In an almost carbon copy of events over the past three days, tugboats tried to use their immense pulling power to free the tanker, which was carrying 85,000 tonnes of fuel oil, but those efforts failed.

Ultimately, salvage experts brought another tanker alongside, the El Nabila, and transferred roughly 22,000 tonnes of cargo. On the third day of the grounding, and lighter after the transfer, tugboats were able to free the Tropic Brilliance and reopen the canal. The grounding triggered what, until then, was one of the longest closures of the waterway in years.

But lightering the Ever Given would be a completely different matter. The boxship is carrying thousands of containers. If salvage experts need to move the same proportion of cargo as they did to free the Tropic Brilliance, it would entail physically removing, one by one, about a quarter of the boxes, an operation that would take days.

Two Options

The two main options for this lightering process would either be huge cranes that sit atop barges, or powerful helicopters that could take off the boxes -- each one potentially holding up to 22 tons of cargo.

Neither is an easy solution. Heavy-lift helicopters are hugely expensive and deciding the issue of who pays for them would need resolving too. The crane option isn’t straightforward either. There are relatively few barge cranes big enough to lift boxes from such tall ships, and again, it’s arduous.

“It just takes a lot of time and energy,” said Joseph Farrell III, director of business development at Resolve Marine, a company that offers salvage services, who declined to comment about Ever Given specifically. “It can be quite dangerous too because you’ve got to get people to climb up on the containers and actually rig each container and lift them off.”

There’s precedent for just carrying on with the digging. In 2016, a similarly large container ship became stuck in Germany’s Elbe river. What followed was a week of intense dredging around the vessel by SMIT -- the company employed to dislodge the Ever Given. That operation succeeded after about a week.

But if helicopters were eventually to become necessary, then that would be hugely expensive. They cost an upfront fee and an hourly rate that can get up to $20,000, according to Farrell.

The lifting can only be performed by a special type of aircraft called sky-crane helicopters that are able to haul loads of 25,000 pounds (about 12.5 tons), according to Nick Sloane, the salvage master responsible for re-floating the Costa Concordia, which capsized off Italy in 2012.

Finding the right helicopters is a task in itself, said Keith Saylor, director of commercial operations at Aurora, Oregon-based Columbia Helicopters Inc., a company that provides commercial heavy-lift helicopters.

Many, like the Chinooks that are part of his fleet, are owned by governments or the military, who seldom participate in salvage missions. The U.S. has offered to help the Suez Canal Authority, although it’s not clear what that assistance might extend to.

A few suitable helicopters are privately-owned and most of those are in the U.S., almost 7,000 miles away, Saylor said.

“If you can’t find one near the Suez canal you’d need to fly them over,” he said by phone from Phoenix, Arizona.

Just the cost to transport the helicopter is estimated at $1.7 million. Finding the right pilot to fly it isn’t easy either. There are probably no more than 100 in the world who are trained for such a task, Saylor said.

Barges

Each container could be removed at a 5-minute clip, according to Saylor, so over a period of 12 hours 144 containers could be removed. The Ever Given can carry about 20,000 steel boxes.

The other option is so-called crane barges -- specialist vessels that could be used to lift cargoes off. But since the Ever Given is one of the largest ships of its kind in the world, it would need a particularly tall crane barge, of which there are few in the world, to do the job.

“It is concerning that they haven’t gotten her out yet,” said Alan Murphy, CEO of Sea-Intelligence. “If there’s news that the hull has been breached, or they need to evacuate the boxes to get her free, then it’s a big-time problem.”

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