Q: How does a person carry out their salaah on a plane? Does it have to be re-read once a person lands? Is it true that a persons wudhu will not break if they sleep while sitting if their feet is on the ground? ( eg in flight)
A: If it was performed in the right direction with proper postures then it does not have to be re-read.
If it was just a moment of slumber where you were more or less in control of yourself then this does not break wudhu. A deep sleep breaks the wudhu.
And Allah Ta’ala (الله تعالى) knows best.