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.
3. Re: cost to upgrade to economy comfort on delta. Apr 19, 2014, 8:59 PM. Usually you buy your normal economy ticket and then when you are choosing your seat on the Delta web site if you hover your mouse over an Economy plus seat it will tell you how much it costs. It is a separate transaction from buying the ticket.