Are you studying for a law school property test?:)

You would have to get a survey of the possible air rights that each of you have in your area to find that out.

Unless there is some kind of easement in existance you own as high as the sky, as far up untill there is no more up. Your bridge might have been a facetious crossover but your 'up' property rights prevent the power company from putting high tension lines across your lot even if the towers are on other property. Eminent domain requires certain legal proceedings and some folks do beat city hall.I know of two businesses in Dallas that are under freeway overpasses, one of them I know was there before the freeway.I don't know what kind of legal stuff all concerned went thru, In a way it seems a good deal,the building is protected fro.m the elements, but then the overpass could collapse. I presume that when you learned about 'down' you heards about the 'cone'. Since the Earth's surface is curved, everybody's property lines converge at the center of the earth. Similarly every one's up lines spread out, so at some infinitesmally small distance above the ground your and your neighbor's air rights start overlapping.Higher up evryone's property is overlapping. And of course the Earth is spinning and moving around the sun, and the sun and galaxy are moving, so your property is just moving all over the universe. But practically and legally speaking you own up as far as you can see. There are some legal and practical exemptions, so don't get to pondering about putting up a toll gate and charging the airlines to fly over your house.

Typically you own from the center of the earth to the strasosphere. So the answer would generally be "NO!"

I'd be more concerned with how far DOWN you own. Now that is not always a simple answer. It takes reading your deed very carefully. I was surprised to find that we didn't own all of our underground of our property and that some family that lived out of state owned it from back in the early 1900s. I bet they didn't even know about it but it was right there in our deed. Land rights are different than water, gas, and mineral rights, especially in the Western part of the US.

Is'nt it everyones right? New legislation in the air dear I fear we should look into building houses into some of the the existing arches and spaces within bridges. Services moving horozontily. Not all waters are rising, are they? Keep neighbours bridged

You (in the US) only own the area above your property to the height that belongs to Government air space. Each area may be different, depending on air traffic, local zoning etc. In Las Vegas, the Stratosphere tower was reduced several feet from the original plans by air lane restrictions. It is also determined that you only own the air above that you can reasonably use. A neighbor would not be allowed to run a bridge over you, however the government could.