The Eckener Alternative by James L. Cambias which originally appeared in All-Star Zeppelin Adventure Stories.
The story isn't Steampunk but it involves a quest for a world where airships never disappeared from the skies. What's the harm in that?
“You can’t make big changes,” said the instructor the first day of
Temporal Studies class. He was a very laid-back physicist recruited
from California in 2020s. “That’s the most important rule. The folks
we work for are the result of a particular set of historical
events. Change history too much and their probability level drops below
50 percent. If that happens, all this” — his gesture encompassed the
Time Center — goes away and we’re out of a job. If we even exist
A student in the row ahead of Cavalli raised his hand. “What about making little changes?”
“Little changes are fine. We make little changes all the time.
Most of them are things like making long-term investments, buying up
art treasures for safekeeping, keeping species from going extinct, that
kind of thing. You’re going to learn all about gauging the effect of
changes, avoiding heterodynes and chaotic points, and when it’s okay to
step on butterflies.”
Cavalli was listening, but in the margin of his notebook he was doodling airships.