Japan Travel Bureau, the country's leading travel agency, will start full-scale sales of discount overseas flight tickets beginning Feb. 16 to cope with the growing market for nonpackage-tour travelers, a spokesman for JTB said Thursday.

JTB will sell discount tickets at some 634 branches of its own and its affiliate, JTB Traveland, Inc. The tickets will cover departures on April 1 and later.

JTB's entry is expected to set off a high-stakes war over the discount air ticket market, which has so far been dominated by H.I.S. Co. and other latecomers to the travel agent industry that have flourished since the 1980s. The spokesman said JTB's recently upgraded computer system will enable the agency to handle discount fares, which fluctuate quickly, with flexibility and lower personnel costs.