* A work of art that's appraised at $10,000, for example, but that's priced for sale at $5000, is not necessarily a bargain. As stated above, a retail or insurance appraisal can be many times the fair market value of a work of art. Always determine fair market value first, no matter how big a bargain the seller makes you think you're getting.
In general the aircraft must be at least 500 feet away from any person, vessel, vehicle, or structure. In congested areas the aircraft must stay 1000 feet above the highest obstacle within a 2000 foot radius of the aircraft. There are special rules for helicopters that allow them to fly closer than these general limits.
Passengers want to reach their destination quickly, so designers aim at a high cruising speed.. However, passengers also value safe landings, and hence the landing speed should be slow. Speed is the main reason why airliners fly at an altitude above 30,000 feet or close to 10 kilometers.