Easy...
It stays in the hover, assuming the R/C pilot can maintain the hover whilst the 737 is accelerating.
OK, so lets say it's on the deck when the jet rolls, then lifts off when it's in the cruise? Will it still go backwards?
By the way, we wanted to buy two and race them around the cabin, but thought that the crew might not see the funny side.....
But while we are on the subject of hypotheticals, what happens if you are travelling at the speed of light and you turn your headlights on???
It gets very dark.... ?