Delta Air Lines Inc. /zigman2/quotes/200327741/composite DAL -2.75% has amended its $2.65 billion revolving-credit line to extend it and turn into secured debt, it said in a filing Thursday. The newly amended instrument includes a $1.325 billion three-year facility, $1.25 billion of which Delta extended for one additional year to April 2022, a $1.325 billion five-year facility, which matures in April 2023, and a new $216 million standby letter of credit, which matures in April 2022. The amended revolving-credit facility, previously unsecured, is now secured by liens on certain routes and other related assets, with the option of pledging aircraft, among other assets, as additional collateral, the company said. Delta also amended an one-year term loan, and both the revolving-credit line and the term loan require Delta to have a minimum of $2 billion liquidity. Shares of Delta rose 0.6% in the extended session Thursday after ending the regular trading day up less than 0.1%.