It's astounding this is so complicated. And it's astounding so many people don't realise he's looking for a word that fits in the same sentence, or confirmation there is no such word.
HOWEVER cruises take weeks/month whereas flights take minutes/hours.
the closest equivalent (in a sense) to "my flight is at 3PM: is "my cruise is on wednesday". it's usually a little weird to say "my cruise is at 3PM", exactly as it would be a little weird to say "my flight is at 3:13:37.45 seconds"
For more clarity on the three "things" above
airplane 'Spirit' / flight AF011 / takeoff 14:45
boat 'QE2' / cruise 'SunnyMed17B' / departure 10:00
the simple answer to your literal question is, of course, "my cruise is at 2PM". But bear in mind the "timescale metric weirdness" mentioned here.
note that you can say "my flight leaves at.." just as you can say "my cruise leaves at.."