Weight & Balance. @:-) All aircraft, my R/C models, and 777's, have a center of LIFT based on the geomerty of the wings, etc., and a center of GRAVITY based on the empty weight of the airframe, cargo positioning, fuel, and where you sit. When CG is near the CL = ideal. Noseheavy planes do not fly well. Tail heavy planes do not fly at all. Yes, it is less critical at higher airspeeds, because the elevator has more authority to counter imbalances. But that means more drag, too.

Most critical at stall speed, like landing and taking off. The USAF had a Lear jet crash when a fuel transfer control relay stuck, (unknown to the pilots) and slowly kept pumping fuel out of one wing tank into the other wing tank. Eventually the aerodynamic control surfaces couldn't keep up with the gravity imbalance, the plane flipped over, and they all died.

Did you know a full 777-ER like from HKG-EWR has 300,000 lbs empty hull weight, 300,000 lbs. of fuel, some (?) cargo, and only room for 50,000 lbs of passengers and luggage? Distribute that weight in the wrong places, and we all die.

Let's see: 300,000 lbs fuel / 5 lb/gallon = 60,000 gallons * $2.00/gal = $120,000 in fuel alone, / 250 passengers = $480 apiece for GAS!! I'm sure glad those BF customers at $6,000 each are paying for some of my jet fuel in coach as well as for the crew's salaries, and rent on an expensive A/C.

Someone who works for Boeing or CO can probably improve on these numbers.