Look at these examples:
Note that most nouns ending in -al become -aux in the plural.
But as usual in French, there are some exceptions !
Here is a list of the most common ones:
des bals ([dancing] balls),
des régals (feasts/delights),
des chacals (jackals)
Learn more about these related French grammar topics
Examples and resources
"Plurals in French" by www.frenchspanishonline.com
"Les pluriel des noms" by youlearnfrench.blogspot.com