After reading this question, I'm reminded of a short story which involved portals between planets.
The portals were unstable and weren't (couldn't be) anchored to the ground. To travel through one, you had to chase it down in an airplane.
At one point in the story, the pilot is chasing a portal and the portal changes directions and hits the airplane instead of the other way around.
The story wasn't about the portals, but rather about changes in technology and the usefulness/uselessness of learning different skills.
At the end, a passenger on the plane who's been talking to the pilot asks the pilot what he'll do when the portal technology has been improved and can be anchored to the ground and the glamorous job of portal pilot disappears.
The pilot answers "well, I'm not too proud to learn to drive a truck," implying that he doesn't care about the job but rather that he's more interested in the travel.
I read it probably twenty years ago, but it was old even then.
Does anyone know the name of the story and where (in what anthology or collection of short stories) I might find a copy?