The news came midway through United Airlines Flight 231, from Washington, D.C., to San Jose, Calif., on June 3, when the captain summoned Mike Bell to the cockpit. Dakota, Bell was told, his 10½-year-old Basenji, was not in the heated area of the cargo hold reserved for pets. Instead, the dog had been mistakenly put in a dark, freezing-cold baggage section. "The pilot said that he didn't know if Dakota was alive or not at that moment, but that if we continued to San Jose, he wouldn't make it," recalls Bell, 38, a software quality-assurance manager in Santa Clara. "I was speechless. My eyes were getting watery."

Since the crew couldn't get access to the hold during flight, the captain announced they would make an unscheduled landing at the nearest airport—in Denver, still an hour away. "The wait was agonizing," says Bell. "I was thinking the worst. Then I thought about how strong-willed and stubborn Dakota is." When they landed, Bell and the captain went to the tarmac, where Dakota was shivering but okay. With the pilot's blessing, Bell carried Dakota back onboard in his arms. "As soon as I passed the first-class cabin, everyone in coach started to clap and cheer," he says. And after they landed in San Jose, just 30 minutes behind schedule, "one woman was almost in tears," says Bell's pal Dawn Myers, who met the pair at the airport. "She said, 'I'm so glad the dog is okay' " Although Bell wasn't offered compensation, he isn't angry about United's error, which was discovered by an employee after the plane had taken off. "I'm just happy about what the pilot did," he says. "It cost United a lot of money to divert the plane." But the next time he and Dakota travel, he says, "I'll drive or take Amtrak."