The Hótel Loftleiðir, now known as the Icelandair Hótel Reykjavík Natura, appears twice in the production.
Stewart arrives at the Hótel Loftleiðir to book in for his flight to Húsavík. The check-in for domestic flights has in fact never been at the hotel, however the terminal for the buses going to and from Keflavík airport was. There was a conveyor belt on which the luggage was brought into the hotel, which together with the announcements for buses going to Keflavík gave the hotel the appearance of a terminal check-in.
Stewart enters the hotel and walks to the desk located by the souvenir shop, Rammagerðin. He passes the hotel reception, located on his left by the entrance, which looked like this from 1966 for about 20 years. As he stands at the desk talking to a member of staff a Scan West computer can be seen on the desk, this was the first computer system in the hotel. 
Stewart then waits in the hotel cafeteria, which is now the location of meeting room 3.
The hotel features again just after Slade has met Jack Case; they are drinking in the restaurant bar of the hotel then called Víkingasal. This area is now more open-plan and used as a function space also providing lobby access to another meeting room.
The ambitious idea to build an airline hotel formed in 1964, and the Hótel Loftleiðir was completed and officially opened in May 1966. The hotel was later expanded in 1971. The hotel was popular with Icelanders and was a popular venue for meetings and entertainment. The Karls Lilleandahls Orchestra played at dances in the Víkingasal restaurant and the cafeteria opened from 5am to provide breakfast for guests flying to Keflavík airport, also catering for the party revellers who could be provided with French fries and a sandwich before making their way home. 
Today at the hotel, shown in the gallery on this page, you can see unique sculptures made by Aðalheiður S. Eysteinsdóttir, they appear in all of the Icelandair hotels.
Images © BBC Scotland, © The Bagley Brief
1. Helgason, Þ. (2012) pers. comm 20th November, 2012
2. Icelandair Hotels (2015). History of Icelandair Hotel Reykjavik Natura (2015). [online] URL [Accessed Jan. 3rd 2015]