The Understudy Takes the Stage at Apple

On an 18-hour flight from California to Singapore a few years ago, Timothy D. Cook, Apple’s chief operating officer, had little time for small talk with a colleague. Glued to his business class seat, Mr. Cook had his nose in spreadsheets, preparing for a thorough review of Apple’s Asian operations.

The two landed at 6 a.m., took time to shower and headed into a meeting with Apple’s local executives. Twelve hours later, and well past dinnertime, the local executives were ready to call it quits.

“They were absolutely exhausted,” said Michael Janes, the Apple executive who accompanied Mr. Cook. “Tim was not. He was ready to jump to the next slide and the next slide after that. He is absolutely relentless.”

That relentlessness could be indispensable in the months ahead, because Mr. Cook may be tested as never before. He has been charged with running Apple’s day-to-day operations while his boss, Steven P. Jobs, the company’s visionary chief executive, is on medical leave.

Mr. Cook has done that twice before, briefly and successfully. Yet if Mr. Jobs’s health does not improve, Mr. Cook could be on the job for a long time. And while Apple’s succession plans are closely guarded, Mr. Cook is widely believed to be the most likely candidate to permanently replace Mr. Jobs.

In Silicon Valley, Mr. Jobs is also known for relentlessness. Yet on many levels, he and Mr. Cook are opposites. While Mr. Jobs is mercurial and prone to outbursts, Mr. Cook, who was raised in a small town in Alabama, is polite and soft-spoken. He is often described as a “Southern gentleman.” While Mr. Jobs obsesses over every last detail of Apple’s products, Mr. Cook obsesses over the less glamorous minutiae of Apple’s operations.

Their complementary skills have helped Apple pull off the most remarkable turnaround in American business, and made it the world’s most valuable technology company. When Mr. Cook is on his own, he will have to compensate for the absence of Mr. Jobs — and his inventiveness, charisma and uncanny ability to predict the future of technology and anticipate the wishes of consumers.

“He is going to have to look to others to provide the creative vacuum left by Steve,” said A. M. Sacconaghi Jr., an analyst with Sanford Bernstein & Company.

Mr. Cook and Apple declined to comment for this article. From his first days at Apple in 1998, Mr. Cook, who is known as intensely private, worked in the shadow of Mr. Jobs and other prominent leaders. Although his job — making sure Apple could produce, assemble and ship its breakthrough products around the world, and do so profitably — was not considered sexy, he quickly removed inefficiencies from Apple’s supply chain.

“My favorite scenes were meeting suppliers,” said a former Apple executive who had traveled with Mr. Cook frequently and asked to remain anonymous because he did not want to upset their relationship. “He is Mr. Spreadsheet. If things weren’t right, he would torture the suppliers and demand improvement. At the same time, he had good relationships with them.”

Apple was smaller then and largely focused on making PCs. Its operations were a mess.

Apple was still running its own factories in California, Ireland and Singapore. While more profitable and efficient companies like Dell had moved to a just-in-time manufacturing model, Apple still held 90 days of inventory.

Mr. Cook closed Apple’s factories and outsourced all manufacturing to a far-flung network of suppliers in Asia. Inventories decreased to 60 days, then to 30 days, then to the just-in-time model. Mr. Cook virtually lived in airplanes, traveling the world to meet with suppliers and browbeat them into meeting his demands.

Analysts and investors say Mr. Cook’s efforts on the production end made the difference in turning Apple’s fortunes around. And they still are critical to the company’s success.

Take the iPad. It took Mr. Jobs’s imagination and the expertise of his engineers and designers to create it. But Mr. Cook’s operational abilities allowed Apple to parlay a cool product into a business that has already brought in $9.6 billion, as the company built and shipped worldwide nearly 15 million iPads in just nine months to meet customers’ seemingly insatiable appetite.