President Masoud Pezeshkian of Iran on Friday met in Moscow with Vladimir V. Putin, his Russian counterpart, for high-profile talks, solidifying an alliance between two countries driven by a mutual desire to challenge the West.

Iran and Russia have been subjected to numerous sanctions by the West, and trade and finance are at the forefront of a strategic cooperation agreement that the two leaders are expected to sign.

The agreement is also expected to cover military issues, but in contrast to accords that Moscow has signed with other allies, the deal with Iran stops short of including a mutual defense clause, according to Iran’s ambassador to Moscow.

“Our country’s independence and security, as well as self-reliance, are very important,” Kazem Jalali, told IRNA, an Iranian news agency, according to TASS. “We are not interested in joining any bloc.”

Speaking in the Kremlin ahead of the meeting, Mr. Putin called Mr. Pezeshkian’s visit “especially important” because of the “big, basic, comprehensive, strategic cooperation agreement” that they planned to sign.

Before Mr. Pezeshkian’s arrival, Dmitri S. Peskov, the Kremlin’s spokesman, said the signing of the treaty would be a “very important event” for Russia, and Iranian leaders have portrayed the trip as more than just a state visit, saying it represented a strategic turning point.

“This treaty is not only a key turning point that strengthens our bilateral ties,” wrote Iran’s foreign minister, Abbas Araghchi, on the social media network Telegram. He added, “This is not just a political agreement, it’s the road map to the future.”

Mr. Peskov said that the timing of the treaty’s signing was not meant to divert attention from the inauguration on Monday of Donald J. Trump as president in the United States, and Mr. Araghchi told state television in Iran that it had been scheduled months ago.

Since the invasion of Ukraine nearly three years ago, Moscow and Tehran have been growing closer. Iran has sent short-range ballistic missiles and drones to Russia, according to U.S. and European officials, to aid the Kremlin’s war effort. Iran has denied it is providing weapons to Moscow.

The Kremlin has provided some diplomatic support to Tehran, but has had to balance the relationship with maintaining ties with Saudi Arabia and United Arab Emirates, both of which are opponents of Iran. Both Moscow and Tehran have recently faced a major setback in the region with the fall of Bashar al-Assad’s regime in Syria.

Since the start of the war, Russia has been working to counter what it sees as an aggressive and imperial Western hegemony, led by the United States, by creating and formalizing a series of treaties.

In June, Russia signed a partnership agreement with North Korea, and in December, a security treaty with Belarus formalized the deployment of Russian tactical nuclear weapons in that country. Both treaties included a mutual defense clause.

Russia also leads what is known as the Collective Security Treaty Organization, which includes Belarus and several other former Soviet states including Armenia in the Caucasus, and Kazakhstan, Kyrgyzstan and Tajikistan in Central Asia. Intended as a counterweight to NATO, the organization is based on a principle that an attack against one member should be perceived as an attack against all. The alliance has been challenged recently with Armenia effectively freezing its membership.

For its part, Iran is facing a cascade of challenges at home and in the region, with its militant allies weakened and its economy in shambles because of sanctions. The return of Mr. Trump as U.S. president will likely bring more pressure and efforts by Washington to isolate Iran.

Apart from defense issues, Russia has been working with Iran and other countries to develop an alternative to the Western-led Swift, a global messaging service that connects more than 11,000 financial institutions and allows them to alert one another about pending transactions.

Moscow also hopes to build a railway through Iran that would connect Russia directly with ports on the Persian Gulf. Mr. Araghchi said that the deal to be signed Friday would allow Iran to serve as a passageway for Russian gas exports through its network of pipelines, bringing gas from the Caspian Sea to the shores of the Persian Gulf. It means, he said, that Iran is “becoming a major hub for gas exports.”

Mr. Jalali, the ambassador to Russia, told Iranian media that the leaders of Russia and Iran realized that an older agreement between the two countries was outdated and did not reflect the realities of the current world and regional order.

The new accord, he said, “takes into consideration every aspect of our bilateral relations including our political posturing. How do we view power and how do we move forward together.”

It is almost over, the end so close they can practically feel the keys they have kept all these months sliding into the locks of their old homes, the doorknobs turning in their hands, the beds they will sink into for their first night’s peaceful rest in more than 15 months — their own beds. Just a couple more days to go.

Two nights before the first stage of a cease-fire in Gaza was announced, Layan al-Mohtaseb, 15, dreamed of being back in her bedroom in Gaza City, cleaning it as she used to before her family fled during the war.

“This time, it feels like we’re truly going home,” she said.

That may be true only for those whose homes are still standing after months of destruction. And there is always a chance the fighting might resume after the six-week initial truce if talks over a permanent one collapsed. But across Gaza, people were daydreaming of the first moments of peace, the people they would hug as soon as the truce took hold, the graves they would visit. They already knew they would be shedding tears, tears they hardly knew whether to attribute to joy or to grief.

If Wednesday night was for celebrating the news that a cease-fire deal had been struck, the following days were for making preparations. As the Israeli security cabinet convened to vote on the cease-fire and hostage release agreement on Friday, Palestinians were calling around for trucks they could rent to move their things back to northern Gaza, or vans, or even donkey carts; they were packing up their tents, wondering where they would live if their houses were no longer there.

Fedaa al-Rayyes, 40, was already buying ingredients to make small festive sweets to welcome the war’s end. But the first thing she planned to do when the bombs and drones fell silent was to search for relatives she hadn’t seen in months, to find out who was still alive and to mourn for those who did not live to see this day.

“It’s impossible to describe this mix of relief and grief,” she said. “I’m happy we survived and grateful for the kind people who helped us. Yet, I’m deeply sad — sad for the relatives and friends we lost and for the neighborhood we’ll return to without them.”

There were practical matters to think of, too. She would remind her children to “stay away from anything that might still be dangerous or explosive,” she said — from all the unexploded ordnance littering Gaza that could keep adding to the war’s casualty count, one accidental blast at a time, for months or years to come.

Most of Gaza’s population of more than two million people have had to huddle into tents and schools and other people’s apartments for much of the war, driven by Israel’s airstrikes and evacuation orders from their houses or the earlier shelters they had tried. Now they could think of little else but going home. Even if those homes were damaged. Even if they were now no more than rubble and ash.

Manal Silmi, 34, a psychologist for an international aid group, planned first to go hug her mother and her siblings and “cry, letting out all the pain we’ve carried for these 15 months,” she said.

Then the trek home could begin. Per the agreement, people displaced from northern Gaza to the south will be allowed to return on the seventh day after the cease-fire takes effect on Sunday. Her family was already looking for a big van to drive all their tents and bedding back up north. Her friends and the few relatives she had left in Gaza City had already called, making plans to meet them at the crossing point dividing northern and southern Gaza.

“We’ll hug, we’ll cry and we’ll thank God over and over for surviving this war,” she said.

Al-Hassan al-Harazeen, 23, a college senior majoring in computer science, knew his family’s house in eastern Gaza City was in ruins, he said. But he would still head straight there as soon as the cease-fire began.

He was imagining spray-painting his family’s name on any brick that was still in one piece, picturing himself sitting on the rubble for a while, he said, “to embrace those broken stones and bricks as if they’re a part of me.”

Then he would visit the grave where they had buried his grandfather at the start of the war to recite the opening verses of the Quran for him.

Even as mediators announced the deal on Wednesday, Israel was still heavily bombing Gaza. Two of Jamal Mortaja’s employees from the solar-panel business he owned before the war were killed the day before. They would be in his thoughts, said Mr. Mortaja, 65, when he headed back to Gaza City to visit what remained of his home before checking on his stores at the al-Ansar roundabout.

Raed al-Gharabli, too, wanted to return to Gaza City, despite his home’s destruction, just to say goodbye before the rubble was removed. He wanted to walk through his neighborhood, Shuja’iyya, greeting neighbors who had stuck it out all these long months. He would take his makeshift tent from the central Gaza city of Deir al Balah, where he had fled with his family, and set it up next to the ruins of his house.

“I can’t wait to see this moment become real,” said Mr. al-Gharabli, 48, a tailor. “If I could, I’d fly straight north and land on the rubble of my home.”

To speed things up, he said his family would leave some belongings with neighbors in Deir al Balah, where they and other displaced people had come to trust and rely on people who had been total strangers at the war’s beginning.

There was even a part of them that was already nostalgic for it, the camaraderie that had formed between them and their temporary neighbors.

After his home in the southern city of Khan Younis was destroyed, Ismail al-Sheikh, 39, a university lecturer, had moved to a tent nearby, where he got to know two men in nearby tents. The new friends spent their evenings reminiscing about life before Oct. 7, 2023, when the war began, and imagining aloud what would happen once the nightmare was over. What they would do. Where they would go.

For Mr. al-Sheikh, who taught at al-Aqsa University, the daydreams were nothing crazy. He just wanted his normal life back, teaching his classes, meeting up with friends at night at the Titanic Restaurant in Khan Younis. The Titanic, which he’d heard had collapsed into rubble.

Now, with the war nearing its close, his new friends were getting ready to return to Gaza City, where they were from.

“I’ll deeply miss those gatherings,” Mr. al-Sheikh said. “It’s truly a mix of emotions — happiness for their return, sadness for the farewells and hope for what lies ahead.”

The cause of the fatal plane crash in South Korea last month is still to be determined, but it thrust into the spotlight a subject little understood by the general public: how airplanes are maintained.

Jeju Air, the airline that operated the flight in which 179 people died, said that checks before the flight had raised no concerns and that the jet, a Boeing 737-800 that was about 15 years old, had no history of accidents.

While there is no evidence that poor upkeep played a role in the crash, experts say that the plane’s repair history, which includes work performed by maintenance firms in other countries, will be an important part of the crash investigation, as is typically the case.

Here’s what you should know about how airplanes are maintained.

The Basics

Airline executives, pilots, mechanics, regulators and others play vital, and overlapping, roles in taking care of commercial jets.

At the front line is a practice that will be familiar to many travelers even if they don’t know what it is called: line maintenance, which involves regular inspections and repairs between flights. Before a jet takes off, pilots perform visual and other inspections for damage or other problems. Airline mechanics also conduct periodic checks. Often, a mechanic can troubleshoot a problem quickly, fixing it or safely patching it up until the issue can be addressed later. Serious problems can result in a long delay or cancellation.

In addition, every part of a plane, down to the nuts and bolts, is subjected to routine inspections, repair or replacement. Those checks are typically scheduled based on how many hours the plane has been used, the number of flights, time or some combination of those factors. These inspections are overseen by aviation authorities around the world, with many following the lead of regulators at the Federal Aviation Administration or its European Union counterpart.

When it comes to more intensive maintenance that might take a plane out of service for days or weeks, the world’s largest airlines perform much of that work on their own. Some, including Lufthansa and Delta Air Lines, even sell those services to others. But every airline outsources at least some work to the companies that make parts and planes, like Boeing and Airbus, or to third parties. Small carriers, especially, depend on the practice.

“If you look at the long tail of aircraft operators, the majority are very small, so it never made sense for them to invest the capital,” said Jonathan Berger, a founding partner of Alton Aviation, a consulting firm. “Outsourcing has been going on since the dawn of time.”

The Rise of Outsourcing

While it has always played a role in aviation, outsourcing accelerated in recent decades. In the United States, the share of spending on airline maintenance that was outsourced more than doubled from 1990 to 2011, rising from about 20 percent to more than 44 percent, according to a 2012 Congressional Research Service report. Airlines do not typically disclose such spending and few outside the industry track or estimate it.

Worldwide, airlines still conduct almost all of their own line maintenance. But they often send out more comprehensive work to companies that specialize in maintenance, repair and overhaul of planes. That work is usually divided into three categories, covering the airframe — or body, wings and tail of a plane — the engine and various other components.

Labor accounts for most of the cost of airframe maintenance, so airlines in wealthier countries often send that work to countries where wages are lower. Some U.S. airlines send planes to El Salvador, for example, and Western European carriers send them to Eastern Europe.

With engines, materials make up more of the cost of repairs, so outsourcing to lower-income countries doesn’t save airlines as much. Still, the much of that work is also outsourced, often to engine manufacturers, because fixing these large machines is expensive and complex, according to Mr. Berger. Most jet engines for large commercial planes are made by several U.S. and European companies.

The global network of maintenance providers is a growing market valued at more than $100 billion. Proponents say that it allows airlines, particularly budget carriers, to plan costs and focus on what they do best: plan, sell and operate flights efficiently. Airlines also benefit because they can turn to specialists who may focus on certain kinds of maintenance or aircraft.

Is Outsourcing Safe?

Many aviation industry experts say that outsourcing is safe and necessary and note that the F.A.A. still oversees maintenance of U.S. planes wherever it occurs. But some consumer groups and labor unions representing American mechanics have raised concerns about it.

“There is a quality issue and for the industry to deny that is just false,” said William J. McGee, who has spent decades as a passenger advocate before lawmakers and regulators and is a senior fellow at the American Economic Liberties Project, a progressive group.

In the 2000s and early 2010s, the Transportation Department’s inspector general looked into the F.A.A.’s oversight of foreign and domestic repair stations and found it lacking. Airline mechanics have reported finding obvious mistakes in planes returning from foreign repair shops. And their unions, including the International Brotherhood of Teamsters and the Transport Workers Union, have raised concerns that workers abroad are not subject to the same rigorous standards as those in the United States.

The F.A.A. recently addressed some of those concerns. This month, a new agency rule will start requiring foreign repair sites to carry out drug and alcohol tests of employees who perform certain safety-sensitive maintenance, affecting as many as 977 locations in 65 countries.

“This rule will ensure these employees are held to the equivalent high level of safety standards, regardless of where they are physically located,” Mike Whitaker, the outgoing F.A.A. administrator, said in a statement last month.

Defenders of outsourcing say that oversight by airlines and the F.A.A. today is rigorous, noting that despite a few shocking crashes and incidents, flying on commercial planes is far safer than other common modes of travel, including cars, buses or trains.

Maintenance Needs Are Rising

Despite a substantial slowdown early in the pandemic, air travel came roaring back much more quickly than the industry had expected. Airlines are now eager to expand and upgrade their fleets.

But Boeing and Airbus, the two big jet manufacturers, have struggled to churn out planes. Boeing has had to slow production in recent years, first after two fatal crashes in 2018 and 2019 of its most popular plane, the 737 Max. Last year, it was forced to do that again after a panel blew off a Max jet in flight, and in the fall it largely stopped production of the Max during a seven-week strike.

Airlines have also had to pull Airbus jets from service to carry out unexpected inspections of Pratt & Whitney engines after the engine manufacturer discovered a quality defect. Airbus and Boeing have also struggled with lingering pandemic-era problems, including shortages of parts and skilled workers.

The slow delivery of new planes has forced airlines to use older planes longer, which is safe but often requires more maintenance. Newer engines, which are packed with new technology that makes them more efficient, have also required more fixes and upkeep than expected.

But the number of people pursuing careers in airplane maintenance has lagged behind demand.

“Not only are the airlines hiring, but general aviation is hiring, corporate aviation is hiring,” Chuck Horning, a professor of aviation maintenance at Embry‑Riddle Aeronautical University, said referring to planes used by many businesses to transport people and goods. “And then you’ve got industries that didn’t even really exist when I graduated in 1986, like the space industry and unmanned aerial systems.”