What does 'returning back across the pond' have to do with it?
If you are a serving Flt Lt then you'll get a retention bonus whatever country you are in, if you qualify. If you are rejoining then you won't get it as your IRD won't be at the 38/16 point.
Besides the RAF is very selective now and looks for people with loyalty and long-term commitment, not those who want to get their grubby hands on a few quid.