TEN MINUTES into a recent flight from San Jose to St. Louis, I was reveling in a first-class upgrade and a new Margaret Atwood novel when I felt and heard a powerful thump. The aircraft, which had been gaining altitude, rocked vigorously. The man next to me widened his eyes, asking, “What was that?” Startled murmurs went around the cabin.

The plane started to descend. It didn’t nose-dive, but sank, as if it were going into a landing. No one screamed, no one spoke, no one moved.

A flight attendant bolted from her seat and lurched down the aisle, leaning over the passengers to peer out the windows. The look on her face brooked no questions. And besides, no one was inclined to interfere with her appointed duties at that moment. Bent over, craning her neck to see, she clambered toward the rear of the plane. I suspected she was looking for a fire in an engine. Seconds later, she ran to the cockpit. It’s frightening to see a stewardess run.