It was the Soviet Union in the '30's. The seats were pikes with a cage that dropped down over the top to keep the victims, er, passengers in place.
You can also check out British Airways web site. They have a History site with vintage pictures from all decades they've been flying airliners in. Here's one of the pages:
http://www.britishairways.com/travel/photos-ata/public/en_us
Wicker or bent plywood is probably very close to accurate.
Gene Beaird,
Pearland, Texas