Before: The Lincoln leaves San Diego

The USS Abraham Lincoln left San Diego last November for its latest deployment. The nuclear-powered aircraft carrier, launched in 1988, is nearly 1,100 feet long — approximately the length of three American football fields — and carries around 5,000 sailors and Marines.

The carrier was later sent to West Asia, where it spent months supporting US operations against Iran.

After: What long deployment did to the carrier

When the Lincoln arrived in Thailand, large patches of what appeared to be rust were visible on its hull, particularly above the waterline and along the edge of the flight deck, where fighter aircraft and helicopters were parked.

Captain Dan Keeler, the Lincoln’s commanding officer, said its appearance was expected after such a prolonged deployment.

“It is normal for a long deployment and we’re not going to make further comments,” Keeler said.

“It looks like what it is: a ship that’s been continuously at sea for 286 days,” Euan Graham, a defence expert at the Australian National Security College, told AP after reviewing photographs of the carrier.

Graham said the ship’s appearance could become a “tempting symbol” of the US Navy’s “strategic overstretch and fatigue”. However, he also highlighted the condition of its air wing as a possible sign of resilience under extreme stress.

Why could the rust not be treated at sea?

Carl Schuster, a former US Navy captain who completed three tours on Nimitz-class carriers such as the Lincoln, told CNN that rust along the waterline was not unusual for a ship that had operated continuously at sea for at least 60 days.

Treating the rust would require crews to be lowered to the waterline, sand away the affected material, apply two coats of rust-preventative primer and then add two coats of naval-grey paint.

According to Schuster, the work could not be carried out at sea, particularly during combat operations.

Some rust on the carrier’s upper levels can be treated while the ship is underway. Repairs along the waterline, however, require the vessel to remain stationary and free from wave action.

Removing the rust could take about 30 days

Based on what he could see, Schuster estimated that removing all the rust could require around 30 days of preservation work.

Some critical maintenance may be undertaken during the ship’s stop in Thailand. Schuster said only high-priority work would be carried out during a seven-day port visit.

The bow and forward areas of the hull would be treated first because they take the most abuse when the ship is moving and face the corrosive effects of saltwater, particularly in choppy seas.

“Rust is like a contagious disease. It spreads. So, it is better to deal with it early to contain it or deal with a much larger problem later,” Schuster said.

He warned that rust weakens the steel structures it affects and must be removed before it has a significant impact on components such as decks, walkways and lifelines.

Morale concerns and supply shortages

Rust has not been the only issue associated with the Lincoln’s prolonged deployment.

Reports emerged last month of deteriorating mental health among the crew and shortages of key food supplies. The US Navy downplayed reports of problems aboard the ship.

A Navy official said a crew member went overboard in early August but was quickly recovered, treated by the ship’s medical department and transferred from the carrier for follow-up care. The official did not say whether the incident was considered a suicide attempt.

President Donald Trump dismissed concerns about the length of the deployment, saying it was “not nearly long enough”.

Trump has previously criticised the appearance of rusty US Navy vessels. Former Navy secretary John Phelan said last year that the President would call him in the middle of the night about the problem.

“He has stated to me many times: ‘Shipbuilding, shipbuilding, shipbuilding. Get those ships out of maintenance yards. Fix the damn rust,’” Phelan said at a conference in Maryland.

First full port stop of the deployment

The Lincoln docked at Laem Chabang for a visit expected to last several days, giving its approximately 5,000 sailors and Marines an opportunity for rest and recreation in nearby Pattaya.

Keeler said the Lincoln would head home soon but would need to make periodic stops to replenish supplies.

“There’s no big delay about when we are going home,” he said. “They move us around where they need us to be.”

(With inputs from CNN and agencies)