From LQWiki

The Airplane Rule states that :“Complexity increases the possibility of failure; a twin-engine airplane has twice as many engine problems as a single-engine airplane.”

By analogy, in both software and electronics, it is the rule that simplicity increases robustness. It is correspondingly argued that the right way to build reliable systems is to put all your eggs in one basket, after making sure that you've built a really good basket. See also KISS Principle, elegant.

This article is based, in whole or in part, on entry or entries in the Jargon File.