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.
Basic Information on Upgrades. There are several types of upgrades on Delta and with SkyMiles: - Complimentary Upgrades for Medallion members (Domestic (excluding Hawaii) and select North/South American destinations ONLY) LINK. - Systemwide Upgrades (SWU's) which can be selected as DM or PM Choice Benefits.