When Maggie and Joel are flying to the Aleutian Islands, Maggie's Cessna airplane has a conventional wheeled undercarriage. However, once they have landed, her plane has skids as the undercarriage.
The plane you see Joel and Maggie get out of is a different plane than the one that you see flying through the mountains. The plain flying through the mountains has the registration number N8326A. The plane they get out of has the registration number N4423V. This helps explain why the plain flying through the mountains has no skis, but the one they get out of does. They are different aircraft.
When Joel and Maggie encounter the Japanes man, Joel's rifle is on the left of his pack. When they leave, it is packed on the right of his pack.
Boom mic briefly visible @ 0:38 during the opening scene in Maggie's cabin.