What happens to the *aircraft* the instant it drops it’s payload?

Assume a typical B-17 WWII bomber. We DO NOT need exact, nit-picking calculations on weight. All we need to know is that its total takeoff weight, fully loaded for a bombing run, is X + Y pounds: ‘Y’ being the bomb payload, ‘X’ being everything else (plane, crew, fuel, etc).

Also, assume that in this mission the bomber is dropping all it’s bombs in the same place at the same time (like a WWII “carpet bombing” mission), which I realize is not how it’s usually done today.

Searching the web I found lots of information on the B-17. The technical specs differ between various production models, but I did notice that bomb payload (Y) was about 20% of the total takeoff weight (X + Y). In one example, a pre-production test model for the Army was said to have a bomb payload of 8000 lbs. and a total takeoff weight (fully loaded and armed) of 40,000 lbs. Therefore, I get the rough estimate that, for this plane anyway, the bomb payload represented about 20% of the total weight that could be lifted off the ground. (Please correct me if I’m way way way off base, but no need to nit-pick, these are rough guesses anyway.)

OK, so they’re on their way, locate the target, and “bombs away!” What happens to the flight characteristics of the plane when it (suddenly) loses 20% of its weight? In what appears to be only seconds (albeit 15 or more, if the History Channel has served me correctly), the weight of the plane changes from X + Y to simply X.

What happens to the plane? What does the pilot do to compensate? I assume the plane is going along generating a certain amount of lift. What happens when the “lift to weight” ratio suddenly increases (dramatically)? Does the plane gain altitude, in fact “jump” up in the air? Does the pilot cut airspeed at the moment of the “drop”, effectively reducing the amount of lift being generated? Do they slow to near stall speed just before the drop?

Thanks.