What is the ruling on someone who entered Mecca to perform 'Umrah, arriving by plane, and passed the Miqat without consecrating ihram due to not being ready, then arrived in Mecca without having consecrated ihram, and from where should he now consecrate ihram?

The questioner was obligated to enter into ihram from the miqat by plane when passing it, because he intended to perform the ritual. His ignorance of this is not excusable. He was obligated to return to the miqat to enter into ihram from there. Otherwise, a compensatory sacrifice (dam) is required if he entered into ihram after passing the miqat. However, if he returned before entering into ihram and then entered into ihram from the miqat, there is nothing upon him.