CHICAGO, Dec 2 (Reuters) - Delta Air Lines (DAL.N) has offered a 34% cumulative pay increase to its pilots over three years in a new contract, demonstrating the bargaining power aviators are enjoying in a short-staffed industry with booming travel demand.If the deal is approved by Delta pilots, it is widely expected to act as a benchmark for contract negotiations at rivals United Airlines (UAL.O) and American Airlines (AAL.O).They will also get a one-time payment equivalent to a cumulative 22% of their earnings between 2020 and 2022 after the deal is ratified.The Atlanta-based carrier's pilots have been working without a new contract for nearly three years after their old contract became amendable in December 2019, fueling frustration.In a year of protests for the industry, pilots at all major U.S. carriers have been demanding higher wages and a better work-life balance."