Flight from Danang to N/Trang

Reading earlier the flights are booked out 3 days in advance is this realy the case or not the norm.

Vietnam Airlines booking system is always "sold out". Take the waitlist.
More advice -- domestic flights are always late -- check before you go to the airport.
Vietnam Airlines is OK, really -- they just have these little idiosyncracies.

Also flights to Hanoi book up fast as many travelling prefer it to the train which is really very long (longer then open bus) and mostly at night