 Alaska also used eight Boeing 737 – 200 Combi / QCs to suit the unique needs of flying in the state of Alaska . These aircraft were valued for their ability to be rapidly reconfigured ( hence the moniker QC or " Quick Change " ) to match the specific cargo and passenger loads for any given flight . In the all @-@ freight configuration , the 737 @-@ 200 Combis carried up to six cargo containers , known as " igloos . " The <unk> floor allowed for passenger seating to range from 26 to 72 seats . The 737 @-@ 200s were also gravel @-@ kitted , which allowed them to be used at airports such as Red Dog , which formerly featured a gravel runway . Alaska replaced the 737 @-@ 200s with six reconfigured 737 @-@ 400s between 2006 and 2007 . Five feature a mixed cargo / passenger " Combi " arrangement , and one is a " freighter " carrying only cargo . Unlike the 737 @-@ 200 Combi , the 737 @-@ 400 Combis feature a fixed seating capacity of 72 seats . The last 737 @-@ 200 Combi ( short for combination ) was retired in 2007 and is now displayed at the Alaska Aviation Heritage Museum . 
