Nocte Volamus & Non est sine pulvere palma

[forever young]

my family crest's motto is "Nocte Volamus" or "Non est sine pulvere palma" does anyone know what this means?

 

[Andy]

1. We fly by night
2. There is no achievement (based on the extended use of 'palma') without dust/sand.

May I inquire how the crest has two mottoes?