Is the prayer valid on an airplane while sitting?

The questioner : All right, Shaykh, if you please, is it valid for me to pray on the airplane while I am sitting?

The Shaykh : Yes, indeed, praying on the airplane while you are sitting is valid. If it is a voluntary prayer, there is no harm; if it is a voluntary prayer, such as the witr, for example, there is no harm.

The questioner : As for the obligatory prayer.

The Shaykh : The obligatory prayer is not permissible; you must pray standing. However, if you can reach the airport before the time for prayer ends, do not pray on the airplane, because the prayer on the airplane does not allow for the performance of the pillars and conditions in the required manner.

The questioner : Okay.

The Shaykh : If the journey is long, and you cannot reach the airport until after the time for prayer has ended, then pray at that time, and it is obligatory for you to stand.

The questioner : It is obligatory that.

The Shaykh : you stand, and that you face the qiblah, and that you bow and prostrate to the extent of your ability.

The questioner : Yes.