Is it permissible to enter into a state of ihram from Jeddah for Umrah after spending the night there, given that arrival will be by plane without ihram, and if not permissible, from where should one enter into ihram, and from where should one enter into ihram for subsequent Umrahs?

If you are not determined to perform Umrah, then you are not required to enter into a state of ihram on the plane when you are parallel to the miqat. Rather, you would enter into ihram from Jeddah if you intend to perform Umrah later. However, if you are determined to perform Umrah, then it is obligatory to enter into ihram from the plane when you are at the miqat, and it is not permissible to delay it until Jeddah.

To perform a second Umrah after completing the first, you exit to the hill (area outside the Haram boundary) like Al-Taneem, and enter into ihram from there.