It is permissible to offer voluntary prayers atop one’s mount when travelling, no matter what direction it is facing Sahih Muslim 700 b
Arabic hadith text
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو خَالِدٍ الأَحْمَرُ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَيُصَلِّي عَلَى رَاحِلَتِهِ حَيْثُ تَوَجَّهَتْ بِهِ .
Translation
Ibn 'Umar reported that the Apostle (ﷺ) used to pray on (the back of) his camel in whatever direction it took him.