The Dallas-based airline says it's making the change to help protect passengers who have severe peanut allergies.

Peanuts have historically been the one snack perhaps most linked to airline service. That's especially true at Southwest, which has used peanuts as part of its marketing over the decades. Among its efforts, the low-cost carrier has suggested those booking its cheapest fares were essentially flying for peanuts.

Underscoring the connection, Southwest's corporate blog once went by the name "Nuts about Southwest." Even a 1998 book about the company was titled, "Nuts!: Southwest Airlines' Crazy Recipe for Business and Personal Success."