A quick google didn't show me the answer to this one, but it seems like it'd be a standard physics-class puzzler. Anyone got a definitive answer?

Assume you have an airplane that can only carry 100 pounds of cargo.

Suppose its cargo today needs to be 200 pounds of parakeets.

Can you solve the problem by keeping at least half the parakeets flying around in the cargo hold the entire time?

Does the problem change depending on whether the cargo hold is pressurized or vented to the outside air?