A long trip, a voyage, an adventure, a vacation, and others.
A six letter word for a long trip or journey is voyage.
Journey or expedition.
Crossing and cruise are both synonyms for long journey.
A voyage is another term for long sea journey.
trip
voyage
They had a long journey ahead of them. Will you join us on the journey to Spain?
Haul
The word odyssey is related to odysseus journey because the word odyssey means a long journey and odysseus journey home took him 20 years
Trip
journey ... voyage ... trip
Fare
adventure