greenbears

does it actually cost airlines more money if the passengers weigh more?

let's say a 737 has 100 passenger... 100 passengers at 175 pounds is 17500 pounds total. if the same 100 passengers weigh 225 pounds... that's an extra 5000 pounds on the plane.

will the plane require extra fuel because of the extra 5000 pounds? for example, on a typical nonstop NY to LA flight....

thanks!

Diabo

Yes.

The maximum takeoff weight of a 737NG is about 75.000 kg: 40.000 kg of airplane and 35.000 kg of fuel, passengers, cargo, etc.

The maximum fuel capacity is 20.000 kg. If the tanks are loaded to the max there's room for 15.000 kg of paying weight (pax, cargo), so 5.000 pounds of extra passenger fat will cost the airline quite a lot of money because of higher fuel burn/lower cargo capacity/reduced range.

Christopher

Yes, a plane full of heavy people would use more fuel than a plane full of light people. Whether the occasional particularly heavy passenger in an average group of passengers makes a significant difference must be doubtful. Of course, the average weight of people is increasing (in the rich world), so that is I suppose a consideration too.

B747-437B

The simple answer is "yes", but the accurate answer should be "maybe".

Fuel burn is directly proportional to TOW in almost every case, but TOW is a sum of DOW, fuel and payload. DOW is a constant while fuel/payload are variables. Fuel is a cost center and payload is a revenue center. Hence, there are scenarios where the standard proportionality argument does not always hold true.

nerd

Remember, we're not all airline ops nerds - what is the D.O.W.?

B747-437B

DOW = Dry Operating Weight

CPRich

Basic laws of physics dictate that moving a greater weight over a given distance requires more energy. I don't think airlines have figured out how to work around these laws.

B747-437B

Yes, but the point I am making is that just because the passengers physically weigh more doesn't mean that the airline is actually carrying more weight, and even if they are carrying more weight it doesn't mean that it is costing them more to do so. There are other variables at play here which can skew the argument, ranging from price of fuel at different stations, tankering strategies, cargo payloads, weather and minima reserves, etc...

There is no argument about the laws of physics. It takes more energy to move a heavier plane. The COST of that and its relationship to PASSENGER weights is the tenuous link in the chain.

BarbiJKM

But don't forget to factor in the weight of the luggage as well. A 150 pound person who brings two checked bags at 50 pounds each plus carryon is carrying more weight on the plane than a 225 pound person who doesn't check any luggage.

tommyleo

I'm really trying to understand what you're getting at here. But I can't understand how a plane with heavier passengers doesn't weigh more (and burn more fuel) than if those same passengers were all 50 pounds lighter.

nerd

Me too. The marginal effect is of more weight is more fuel burned, and more cost.

thebat

There is probably an optimum weight for aircraft. So a plane flying a little 'lighter' may not be as efficient as a heavier one.
This is just conjecture, I'm

B747-437B

Passengers only make up a small percentage of the total weight of the aircraft. The rest of the weight is made from the aircraft and its equipment, fuel and cargo.

If the prescribed optimal TOW is 100,000kg (with a DOW constant of 60,000kg) for example this can be attained by 10,000kg of passengers; 10,000 kg of cargo and 20,000kg of fuel --- or by 10,500kg of passengers; 10,000 kg of cargo and 19,500kg of fuel.

The fuel burned will be the same as the total weight being lifted is the same (and therefore the cost will be largely the same), even though the weight of the passengers is higher.

Diabo

Flying lighter does not make planes burn extra fuel. Below optimum weight you're still better off, even though the amount of fuel saved is not proportional to the weight of the fat left behind. Fat passengers always cost more money, no matter how you try to spin the math.

tuamater

On a flight to Tanzania from the US, I once had a very densely packed bag full of supplies, and had to publicly cull personal items from my suitcase in front of everyone standing in line at the check-out desk, in order to save myself from an absurd fine for having one bag that was 10 pounds overweight. I ended up transferring heavy items from the suitcase to my carry-on bag to avoid the charge. How dumb is that?

Some airlines have aggressively worked at getting newspapers and magazines cleared from airplanes after each flight (due to their weight) as a cost cutting measure to save fuel. Most humans weigh a lot more than a pile of magazines. Obviously, weight is a factor.

Here's a solution that will protect everyone's privacy and make the system fair:

--Each passenger gets on the scale along with their suitcases and all carry-ons. No one knows the weight of the passenger, since only the combined weight is calculated.

--Allow passengers traveling together to combine their weights (so a family with toddlers will most likely save -- even when you factor in the stroller). Passengers whose total weight is under the limit get a credit (slender as it may be). Those over the weight limit get an up-charge.

Why should this be so politically incorrect?

Another issue: How accurate are airport scales?