Aircraft

Because you must have water available to form ice. These planes are dry...and so am I!

Because the water had been converted to hydrogen to give better fuel mileage to the plane.

Perhaps it will happen eventuallly. But not in my lifetime!

Actually, ice does form on the aircraft. That's why all high-flying aircraft are equipped with de-icing systems; to melt off accumulated ice before it adds too much weight to the aircraft. Having said that though, it should be noted that the freezing point of water is much lower at the low pressures found at such altitudes, so the aircraft surface must be extremely cold for icing to take place.

Because the air is dry. All the clouds are at lower altitudes.

It depends upon atmospheric conditions. If the air has capacity for more evaporated moisture, then any ice will evaporate. If the air is saturated, then ice crystals will form in clouds. Snow being heavier than air, it falls.

There is a good article in Wikipedia on psychrometry and the properties of air, for further reading.

Thanks a lot Mr. PWSlack...... It seems to be the correct explaination and answer to me .

Regards,

NKRAO wrote: "Thanks a lot Mr. PWSlack...... It seems to be the correct explanation and answer to me."

It IS the correct answer NKRAO.

The adiabatic lapse rate is about two degrees for every thousand feet of altitude gained.

Those plane typically fly at 30,000 feet and higher which means that at altitude the air temp is at least 60 degrees colder than whatever the temps are on the ground below.

If the ambient temp on the ground below is 25 degrees, the outside air temp at 35,000 feet will be 70 degrees colder or about 45 degrees below zero, way too cold to support any moisture, without which ice can't form.

This is one reason why it rarely ever snows on the ground when the outside temps are really cold like below 10 degrees; there's no moisture to turn into snow.

The anti-icing equipment used on aircraft equipped for use in instrument conditions, are designed for those periods of flight when the aircraft is climbing to or descending from cruise altitudes.

In order to do so they often risk flying through icing conditions, occurring at lower altitudes and frequently in clouds.

L. J.