This condition is brought on by a lack of vitamin D, which causes the body to be unable to absorb or deposit calcium. Less commonly, it can also be caused by a lack of calcium or phosphorus, but vitamin D deficiency is by far the most common cause.
8 ways to avoid paying an airline change fee. Everyone's been there: having to change a flight and facing a fee that's almost as much as the original airfare. (Change fees can be $200 on airlines like American, United and Delta, and international flight changes can cost up to $450). Most of us have resigned ourselves to paying the fee of changing our itinerary, no matter how far out the trip still is, but you shouldn't have to.
Fly Guy: How to dodge costly airline change fees. It now costs $200 to change or cancel a non-refundable airfare on the remaining legacy U.S. airlines (American, Delta, United, and US Airways), and a bit less on some other carriers. Changing or canceling an international airfare can cost much more.