It didn't help that River was a flirt.
Sometimes he was actually happy to see her, mostly because she flirted with him and batted her pretty eyes for a cup of tea.
But her constant visits to 221B and appearances while they were on cases confused John. Sherlock took it in his stride, never at all surprised to see that curly halo of hair pop up on all sorts of occasions.
Except once.
River had phoned them from a small, local airport, speaking faster than even Sherlock did on his best days. She demanded that they come to see what she explained was "a treat". John was skeptical. Sherlock said nothing, but put on his coat and called a cab anyway.
The cab ride was quiet and calm. John knew where this airport was, but he had never been there. He complained about being hungry and Sherlock mumbled something about takeaway after they got back home. This placated the ex-army soldier and he went back to staring out the window.
They arrived at the airstrip twenty minutes later. John paid the cab driver because Sherlock jumped from the vehicle the instant that it rolled to a stop. In the distance, a lone plane sat on the asphalt. They walked toward it.
As they approached, River stuck her head out the door. "Isn't she beautiful?!"
John gaped. "River, that's-"
"Amelia Earhart's airplane," Sherlock finished for him, sounding for all the world like he wasn't expecting this. "Mint condition, probably stolen within a week of her famous flight."
"John, sweetie, your jaw is bumping against your knees," River cooed, climbing down from the plane. "Don't give me that look, Watson. I'm not keeping this one."
"I should hope not," he grumbled.
Curiosity grabbed Sherlock by the collar and he spent most of the time at the airfield examining the plane, inside and out. John and River had a mildly pleasant conversation about flying the plane.
"I was thinking about installing a temporal distortion array," she said, watching Sherlock flutter around the plane like a bird.
"A... what?"
"A device that tracks time distortions," River explained. "That's what happened to her, really. Sucked into a time distortion over the Bermuda Triangle. It's famous for missing people, as you know. Largest time distortion on the planet."
"Wait, you can't just give her a way out of it," John said. "That's going to change history."
River shrugged. "Better she stay here than go where she ended up."
Sherlock finished his inspection of the plane and River promised to return it immediately. John chided her for the temporal distortion array, but he never did get her to say she wouldn't install it.
A week later, John was online, looking up details about Amelia Earhardt's last flight. Nothing had changed; perhaps the Doctor had managed to convinced her not to change history.
"No," Sherlock replied, when John told him about it. "She didn't install it. They just took Amelia Earhart elsewhere."