how fast!? [question about airplane speed]

If I am in the air, 35,000 feet above the equator and my plane is going 500 mph and I am traveling east. Is my speed over ground about 1500 mph?

You mean due to the rotation of the Earth underneath you?

I think plane speed is measured relative to the Earth’s surface, so if “my plane is going 500 mph” means your going 500 mph relative to the surface of the ground.

If your plane is going 500 MPH, then your speed is 500 MPH. If your plane is going 1500 MPH, then your speed is 1500 MPH. If your plane is going 167834.27483 MPH, then your speed is 167834.27483 MPH.

Aircraft speed is measured relative to the air mass in which it’s flying; i.e., airspeed. If there is zero wind, then your airspeed is 500 mph and your ground speed is 500 mph. If you have a 50 mph tailwind, then your airspeed is 500 mph and your ground speed is 550 mph. If you have a 100 mph headwind, then your airspeed is 500 mph and your ground speed is 400 mph. (I am assuming that 500 mph airspeed is the true airspeed adjusted for density altitude.)

If you’re asking about your speed along your path around the sun, then you have the speed of the rotation of the air mass (call it 1,000 mph) added to or subtracted from your speed depending on which side of the Earth’s rotation you’re on, plus the speed of the Earth along its orbit (about 67,000 mph).

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General Questions Moderator

To clear up your confusion,try thinking about it this way: what time is your plane scheduled to take off and land at each airport?
If you could fly at 1500 miles per hour, than you should be able land at an airport 1500 miles away in just one hour.
The distance from Chicago to Los Angeles is about 1500 miles. But you can’t fly it in one hour.

If you go up in a hot air balloon on a day with no wind, is your speed over the ground closer to 1,000 mph or zero mph?

Answer: it is about zero mph, because the balloon’s speed with respect to the ground and the air mass above it is zero. The rotation of the Earth causes the surrounding atmosphere to move along (more or less) with the ground.

Your misconception appears to be that you assume that the Earth is rotating, and the the atmosphere is not rotating with it. If this were the case, we would not need airplanes. All we’d have to do is to send up people in a balloon and let the Earth rotate under them. Since this does not work, the atmosphere must be moving along with the ground.

This would only let you travel due west, or east if you didn’t mind flights almost 24 hours long. It’s only a slight improvement over the present system and wouldn’t be worth developing the atmosphere-grabbing technology.

…so you’re saying I shouldn’t run along to the gift shop for helium balloons just yet? I’d be ok with going west (or staying put while the earth goes east, or whatever).

I wonder how long I could hold on to the balloon strings for. :smiley: