He forgot to enter ihram on the plane; should he go back to the miqaat and enter ihram from there?
If someone forgets to enter ihram, or was distracted from doing so whilst on the plane, until he passes the miqaat, so he did not enter ihraam, and he wants to go back by car to the miqaat that he passed, is it permissible for him to do that?
Yes, that is permissible. The basic principle is that if a person who wants to do Hajj or ‘umrah has passed the miqaat and did not enter ihram from there, then he went ahead and entered ihram from the place where he is that is closer than the miqaat, he must offer a compensatory sacrifice, but if he goes back to the miqaat and enters ihraam from there, he does not have to do anything else.
Based on that, if we assume that he got on the plane in al-Qasim airport, intending to do ‘umrah, then he landed in Jeddah before entering ihraam, we say to him: Either go back to as-Sayl al-Kabeer and enter ihram from there, or if you enter ihram from Jeddah, you must offer a compensatory sacrifice. End quote.
Majmoo‘ Fataawa Ibn ‘Uthaymeen (21/302)