Three of the four senior positions on the Airport Authority are expected to be filled by locals on the body with no open recruitment. An authority source said yesterday this was due to difficulty in finding suitable outsiders. The vacated posts could be filled by internal transfer or promotion. But whether the post of chief executive vacated by Dr Hank Townsend would be open for competition had yet to be decided, he said. Billy Lam Chung-lun will be acting chief executive when Dr Townsend's contract expires on Monday. The contracts of corporate development director Clinton Leeks and planning and co-ordination director Elizabeth Bosher expire on Monday. Mr Leeks' post would be taken over by Peter C. H. Tam, general manager of the chairman's office, the source said. Ms Bosher would be replaced by Dora Kay, general manager of corporate co-ordination, the source said. And project director Douglas Oakervee, who retires at the end of the year, will be replaced by Kwei See-kan, 64, retired director of the Highways Department.