Travel company Thomas Cook has announced that Carl Symon will step down from his role as non-executive director on 30 September.The FTSE 250 group said Dawn Airey, currently serving as independent non-executive director, will succeed Symon as senior independent director from 1 October."I would sincerely like to thank Carl Symon for his wisdom, support and contribution as a board member and as senior independent director," said group chairman Frank Meysman.Earlier on Monday, the London-listed company had announced a new joint venture with shareholder Fosun International with the aim of developing domestic, inbound and outbound tourism activities for the Chinese market.Thomas Cook shares were up 0.43% to 139.50p at 11:49 on Monday.