Tui has shocked investors with a profit downgrade and Thomas Cook has put its airline up for sale, underlining the pressures being felt by travel operators this year. Shares in the FTSE 100 firm plunged close to a fifth on Thursday after Tui ditched double-digit growth targets and warned profits would be flat this year in a shock announcement late on Wednesday night. Tui, whose brands include First Choice, had been expected to update the market on trading next Tuesday. Smaller rival Thomas Cook said selling its airline would provide "greater financial flexibility and increased resources". It has suffered in the face of weaker consumer demand this year and a sharp increase in quarterly losses. The sale has has been widely mooted for several months. Several analysts believe it is best way for Thomas Cook to pay down a cumbersome pile of bank loans and corporate bonds.