We really don't know what type of plane it was. It could have been a military aircraft.
Ah but I believe we do, it was a Boeing Constellation.
As occurs many times, some of the info presented in posts is a combination derived form the novel and the film. In this case, some have definitely used novel material. For example, while the Constellation is in the film, it looks quite like daylight when it landed. However, the novel says that it was still dark when the plane arrived. The film shows a Constellation; the novel does not identify the aircraft.
