Oct 5 (Reuters) - French trainmaker Alstom's (ALO.EQ) shares plunged 36% on Thursday after the company slashed its free cash flow target. After the market close on Wednesday the group cut its full-year cash flow guidance due to order delays and after a production ramp-up weighed on its cash in the first half of the year. The drop in its share price wiped about 2.6 billion euros ($2.73 billion) from the company's market value.