"To get anywhere, or even live a long time, a man has to guess, and guess right, over and over again, without enough data for a logical answer."
- Robert Heinlein

In the 1939 Lester del Rey story Habit, racing rockets head from Mars to a point above the ecliptic, down to Jupiter and back to Mars.

They'd given out the course that morning. We were to head out from Kor, point straight at Jupiter with a climb out of the plane of the ecliptic, drive down and hit a beacon rocket they were holding on a direct line with the big planet, forty million miles this side of him; that made about an even three-hundred-million-mile course from Mars, out and back, figured for eight days at a constant acceleration and deceleration of two gravities.

Isaac Asimov calls it "the hop" in Marooned Off Vesta (1939):

“You’ve got to expect things like this to happen sometimes,” he said. “Bucking the asteroids is risky business. We should’ve taken the hop. It takes longer, but it’s the only safe way. But no, the Captain wanted to make the schedule; he would go through,” Mike spat disgustedly, “and here we are.”

“What’s the ‘hop’?” asked Brandon.

“Oh, I take it that friend Mike means that we should have avoided the asteroid belt by plotting a course outside the plane of the ecliptic,” answered Moore.

Going above the ecliptic was also recommended to avoid asteroids in Calling the Empress (1943) by George O. Smith:

Her course, as we see it from the Station here, will be a long radius upward curve, slightly on the parabolic side. Like all long-range cruises, the Empress of Kolain will hoist herself above the plane of the ecliptic to avoid the swarm of meteors that follow about the Sun in the same plane as the planets, lifting the highest at the point of greatest velocity.