If you go onto your airlines website it will tell you.
It takes about nine hours less on the way back.
If you are flying direct about 9 hrs, if going via Glasgow (with Monarch) add another 3 hours.
The question is unanswerable in this form as the cruise line, airline, aircraft have not been stated. There could be refuelling stops, change of aircraft, who knows. Please put some thought into the question & you will sensible responses. You could be going by Tiger Moth for all we know!
How much luggage is allowed on a tiger moth I may give it some thought .?
Thanks to Lambie, of Falkirk I got the answer I wanted, I'm much Obliged to him and others.
You got the answer you wanted but how do you know it was the correct one? How do you know they went on the same airline & route as you are going on, or is it some kind of state secret?