Since the 1950s, KLM presents all of its World Business Class passengers with a unique gift: a Delft blue miniature traditional Dutch house. These miniatures are reproductions of real Dutch houses and are filled with Dutch gin, genever. The houses, however, have not always been filled with genever: initially the houses were filled with Bols liqueur, while in 1986 the switch was made to Bols young genever.
KLM started to hand out the houses in 1952 to its First Class passengers. However, with the elimination of First Class in 1993, the houses were instead handed out to all Business Class passengers.The impetus for these houses was a rule aimed at curtailing a previously widespread practice of offering significant incentives to passengers by limiting the value of gifts given by airlines to 0.75 US cents. KLM did not bill the Delft Blue Houses as a gift, but rather as a last drink on the house, which was served in the house.
Every year, a new house is presented on 7 October, the anniversary of KLM's founding in 1919. The number on the last presented house thus represents the number of years KLM has been in operation. There are various special edition houses which are offered to special guests (like VIPs or honeymoon couples). These special edition houses are the Dutch Royal Palace and the 17th century Cheese Weighing House De Waag in Gouda.