PARIS/NEW YORK, Dec 13 (Reuters) – Delta Air Lines looked close on Wednesday to placing an order for 100 Airbus A321neo jets in a boost for the European planemaker as it tries to narrow a 2017 order gap against Boeing, two people familiar with the matter said. The A321neo has a significant lead in market share over equivalent Boeing narrowbody models, but faces potential competition from a new mid-market jet being studied by Boeing and for which the U.S. firm may start seeking offers next year.