April 12 (SeeNews) - US aerospace and defence company Lockheed Martin promises to deliver the first F-16 jet fighter to Bulgaria in 2022 if it strikes a deal with the country this summer; a tender for a 35-year concession for the Sofia airport draws five bids, while Spanish natural gas and electric utility group Naturgy Energy sells its units in Moldova for 141 million euro. Following are these and more of our top stories this week: