Blue skies is the traditional skydiver's parting phrase, wishing someone the clear, calm conditions that make for good jumping. It is used casually in conversation and at the end of messages.
Two uses
In everyday use it is simply a friendly sign-off, sometimes extended to 'blue skies, black death' — a piece of gallows humour about the sport's risks that older jumpers use more than newer ones.
It is also used in memoriam. When a skydiver dies, 'blue skies' appears in tributes as a farewell. Seeing the phrase in that context is common in the sport, and it is worth knowing which meaning is in play before using it.
These pages explain what things are so the language makes sense. They are not instruction and cannot substitute for it — skydiving is taught in person by rated instructors at a drop zone, and anything involving equipment handling or emergency procedures belongs there rather than on a web page.