when going for umrah if flight is landing at Jeddah airport then when and where should ehraam be worn.

People those who going to Makkah from Jeddah their meeqat is Masjid e johfa.go there and do niyat for umrah there.
If one is unable to go to Masjid e Johfa then he/she can make nazr that I will wear my ehram from Jeddah then they can wear ehram at Jeddah and do the niyat there.
Syed Abul Qasim Rizvi