How does a non-traveller complete Salaah behind a traveller?

In a 4 Rakaat Salaah (Zuhr, Asr and Esha Salaah), if a non-traveller (Muqeem) is following a traveller (Musaafir), a non-traveller will follow a traveller until he completes his 2 Rakaats of Salaah. After the traveller makes Salaam, a non-traveller will not make Salaam. Rather, he will stand up and complete the remainder of his 2 Rakaats of Salaah.

In this case, he is categorized as a Laahiq i.e. one who is still considered to be following the Imaam even though the Salaah of the Imaam is completed. Therefore, just as one does not recite Surah Faatiha behind the Imaam, a non-traveller will not recite Surah Faatihah in completing the remainder of his 2 Rakaats Salaah. He will simply wait for the duration it takes to recite Surah Faatihah (approximately 20 seconds) and then complete his Salaah as normal. (Tahtaawi Ala Maraaqil Falaah 1/418-Fataawa Mahmoodiyyah 7/526)

N.B. The above ruling does not apply to a 2 and 3 Rakaat Salaah (Fajr and Maghrib Salaah) as both the traveller and non-traveller perform the same number of Rakaats. There is no change in the number of Rakaats in these two Salaahs.

And Allah Ta’ala Knows Best