All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If a person is a navigator and in his journey he exceeds a distance of what is considered in the customs of people to be a travel, and his travel is for a permissible objective, then he may combine Thuhr and 'Asr and Maghrib and 'Ishaa' prayers, as he is a traveller and the ruling of a traveller applies to him. Ibn 'Abbaas narrated that "The Prophet used to combine Thuhr and 'Asr, and Maghrib and 'Ishaa' prayers when he is travelling.'' [Ahmad] It is also permissible for this navigator to shorten the prayers as Allaah Says (which means): {And when you travel throughout the land, there is no blame upon you for shortening the prayer,…}[Quran 4:101]. However, when he reaches a town where he intends to stay for more than four days, he is then obliged to complete the prayers according to the view of the majority of scholars. This is even when he is not in his original town or country.
Allaah Knows best.