'flight' is a journey by airplane. Sometimes it is also used for 'escape', 'retreat' or 'getaway'. If you want to travel to a secluded spot and be (/spend your holiday) alone for some time. Or the expression 'a flight of stairs' meaning a system of staircases (台阶). But more common is the 'flight by plane'. A specific (/single) plane may also be called 'a flight'. For example: 'flight number CA932' is the Air China plane from Frankfurt to Beijing leaving (/departing /taking off) 20:15. The length of 'trip' depends on your point of view. For some a week is a trip. Others might use it for a tour up to 3 hours. I use it only for the shorter ones, too. To me 'travel' and 'journey' are the same. And 'cruise' is used for travel by ship (/maritime travel). In our time there are few passenger lines left. Most of passenger traffic are 'cruises' with ships 'cruising' on a round-trip between several harbours (/harbors /ports). 'Voyage' is not limited to ships and sometimes used when using a plane. But always for long distance. I think a yourney is called 'voyage' when you want to make it sound longer, more complicated, harder,... Like an expedition or exploration.