L.I. CENTER LACKS AIR CONTROLLERS
FAA has failed to meet commitments to increase number of air traffic controllers in New York region, raising concerns among lawmakers and union officials who warn controllers are being overworked; increase in manpower from 303 positions to 314 was authorized almost two years ago, but number has actually declined, to 281 working controllers, because of problems finding workers qualified enough for busy center in Ronkonkoma, Long Island; 51 of these employees are trainees; shortage intensifies as FAA, under congressional order, authorizes 335 positions; center is so busy that it can take years longer than elsewhere to train newcomers completely; photo; union official Christopher S Boughn and John Walker of FAA comment (M)