1 Leptin is a powerful and influential hormone produced by your fat cells. 2  It plays a key role in regulating energy intake and energy expenditure.
(Upgrades are not available on fares in the L, T, and U range, however, which are the most deeply discounted.) To calculate the price of an upgrade, Delta charges a dollar amount per 500 miles. $50: Up to 500 miles. $75: 501-1000 miles. $100: 1001-1500 miles.
Sharing miles will cost you more than just the miles themselves. Delta charges one cent per mile transferred, along with a $30 processing fee. For that fee, you can transfer anywhere from 1,000 to 30,000 miles per transaction, in 1,000-mile increments. Here's what that means: