Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.

 

He should follow the timings of the country he is flying over. He may pray both Zhuhr and `Asr at the time of any of them and he can also pray Maghrib and `Ishaa’ together at the time of any of them. In this case, he may pray in advance or delay any of those prayers.

Allah Almighty knows best.