They try to keep the mood elegant to coincide with the fares being paid. We didn’t see any jeans or shorts for dinner or in the lounges. The most casual we saw were slacks for men and collared shirt. Many in sports coat on non formal night. Ladies pants suits to non-formal dresses. Formal night is just that with Tuxedo’s/suits and formal dresses short and long. We like having formals nights but also prefer ability to dress down in the dining room.