When must one enter into a state of Ihram for Umrah if arriving from Medina in Jeddah by plane?

It is prescribed for a traveler to Umrah by plane from Madinah to Makkah to perform ghusl (ritual bath), make wudu (ablution for prayer), and don his ihram. After the plane takes off, he should declare his intention for Umrah (talbiyah) before passing the miqat of the people of Madinah, "Abar Ali."