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.
You may purchase miles in 2,000-mile increments, up to a maximum of 60,000 per year. There is no additional transaction fee, but the cost to buy Delta miles is 3.5 cents each. It costs $70 to buy the minimum number of miles, (2,000) and $2,100 to buy the maximum (60,000). There is no bulk discount on miles purchases.