Dear questioner, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.

This religion of Islam is easy in its teachings. It never burdens a soul beyond its capacity. What a Muslim needs is to equip himself with the applications and practices of the Prophet Muhammad (peace and blessings be upon him) to be able to grasp the wisdom of the teachings of Islam. The Companions of the Prophet were pioneers in this regard. When `Umar ibn Al-Khattab was asked the same question, his answer was so logical and precise.

Answering this question, Sheikh Muhammad ibn Al-`Uthaymeen said, 

If they do not pass any of these Miqats, they should locate a place that comes in line with the nearest Miqat and assume ihram from there. If they take a route between Yalamlam and Qarn Al-Manazil, then they should see which is closer and when they come in line with the one that is closer, they should assume ihram at that point.

The evidence for this is that the people of Iraq came to `Umar and said, "O Emir of the Believers, the Prophet (peace and blessings be upon him) stated that the Miqat for the people of Najd is Qarn, but it is far out of our way." `Umar (may Allah be pleased with him) said, "Consider a place in which you come in line with it on your route."

So, he told them to consider a place in which they could come in line with Qarn Al-Manazil and assume ihram. This is how this incident is narrated in Sahih Al-Bukhari. This ruling of `Umar teaches us something important: that those who come by plane with the intention of performing Hajj or `Umrah and pass these Miqats from above or to the right or left should assume ihram when they come in line with any Miqat. It is not permissible for them to delay the ihram until they land in Jeddah, as many people do, because that goes against what the Prophet (peace and blessings be upon him) taught. Almighty Allah says,

(And [for] whosoever transgresses the set limits of Allah, then indeed he has wronged himself.) (At-Talaq 65:1)

(And [for] whoever transgresses the limits ordained by Allah, then such are the wrongdoers.) (Al-Baqarah 2:229)

So, if someone is coming by plane with the intention of performing Hajj or `Umrah, they should be prepared to assume ihram in the plane. When the plane comes in line with the first Miqat, they must assume ihram; that is, they should intend to assume ihram and avoid delaying it until after they arrive at the airport of Jeddah.

Excerpted with modifications from www.islam-qa.com.