I'm assuming airlines that have inflight WiFi can vent these electrons during flight. There's no way the FAA would ever approve a closed-system bit bucket on an airliner. The potential for an explosion is too great, even with today's high-definition bit buckets.

An engine falling off can lighten the load significantly.

may be offset by the grime the aircraft accumulates...

Cecil Adams addressed this one a while back:

http://www.straightdope.com/columns/...en-their-meals

Dont try walking on the Dutch rail tracks today without boots.

MisterNice

I've been on several regional European trains in the past few years where they still do.

oh my.... you can't be serious, right? If true, I hope it's just eastern European trains....

After descending from a high altitude watervapor will condense into liquid..after a long transpac it practically flows out of the roof onto the pax. I think this represents a gain, however small.

There is also probably a "consumption" of oil or a slow hydraulic leak, as well as a loss of rubber from landing

There may also be slight gravitional variations on different parts of the planet that are miniscule but still play a tiny factor. Additionally, as the aircraft is farther from the surface of the earth while flying, it should have a teeny tiny drop in weight at cruise which it gains back on the ground.

The jet engines might always pick up a couple of geese, increasing the plane's weight.

No - this happens in the UK and in mainline stations they tend to have removable platic sheeting between the rails in stations. It is biodegradable so what's the problem? People don't seem to worry about animal waste.

Well, that begs the question, would a photon only have mass when you collapsed the wave function and considered it as a discrete particle? If so, could I increase the weight of a plane by doing a single/double-slit experiment on board?

If I am not mistaken, photons DO have mass. And it was recently discovered that even neutrinos, previously thought to be massless, have mass.

It is my understanding that the 787 has such a system, but that existing airliners do not. That is one of the reasons that the airliner industry gives for recycling a portion of the air, to keep the humidity from being lower than it already is. I read that the reason existing planes don't humidify is that more moisture would lead to more corrosion of the frame and skin, which is not so much of an issue with the composite 787.

The air at altitude is very dry, I believe that ultra long haul airplanes like the 777�s have humidifiers on board supplied by the on board water source. Newer airplanes recycle more cabin air to conserve fuel, airplanes like the DC-9�s or 727�s did not recycle any air, all air coming into the cabin was fresh air from outside.

It is true about the reason to keep the humidity level low to prevent corrosion, condensation can form with higher levels of humidity and the condensation drips down to the belly of the airplane

Because the outside air at 39,000 feet is about �40 degrees F, all airliners have insulation just inside the outside skins, this insulation over time can absorb and hold this condensation creating the source for corrosion and also add weight to the airplane. I have seen some airplanes like the 727�s that had sections of the belly skins replaced because of excess corrosion.

Airplanes are pressurized by taking high pressure air off of the engines, known as bleed air and ducting it into the cabin. The less air they have to bleed off of the engines, the more air is available for thrust, so this is why the recycle more air today than they did in older airplanes, to save fuel. This pressurization air is regulated by valves that let the air out of the cabin called outflow valves.

Dehydration on long flights can be a problem, I try to drink about 12 ounces of liquid every 2 hours or so to keep hydrated.

For those interested, all toilet waste goes into holding tanks where it is pumped out into a special truck when on the ground. All water from the lav sinks and galley drains is dumped overboard via a heated outside drain mast under the fuselage of the airplane, these fluids are atomized into a fine mist and evaporate before reaching the ground.

Blue ice is caused by a leaking lav toilet tank drain seal, so the toilet fluid just leaks out, freezes and stays on the fuselage until the airplane is at a lower and warmer altitude and falls off of the airplane.

Mr. Elliott

This page from Boeing seems to indicate that it's a fuel-efficiency trade-off:

http://www.boeing.com/commercial/cabinair/

See the last 2 paragraphs on the page.