yes, but in an interview, River Raid's creator - Carol Shaw - ( probably the first woman in the business, BTW ) says that it was supposed to be a boat in the original too, and only ended up a plane because with such small resolution ( Atari IIRC had 112x172 ) they couldn't draw a good-looking boat. If you think about it, actually a boat makes much more sense there
read the interview here:
RIVER RAID
Besides, in my clone I have special levels ( 'lakes' ) where submarines chase you around and shoot torpedoes. Now a submarine torpedoing a plane, that would be too far stretched...