European stocks fell for the sixth consecutive session on Tuesday, led lower by Spain's Amadeus and tracking a fall on the U.S. equity market as investors speculated that the Federal Reserve may raise rates as soon as September, Reuters reported. The FTSEurofirst 300 was down 0.3 percent at 1,524.64 points by 0813 GMT after hitting a one-month low in early trade. It tracked Wall Street, where the Dow Jones dropped into negative territory for the year on Monday. Spanish travel IT firm Amadeus was the top faller on the pan-European FTSEurofirst 300, dropping 6.3 percent to 34.36 euros. The fall came as Air France-KLM said it is considering following a move by Lufthansa to levy a charge on tickets booked via third parties on global distribution systems (GDS) as a way of increasing its per-ticket earnings. This drew the ire of Amadeus, which will now have to use a different system to avoid the charge, and the stock is down nearly 15 percent in June. Broker Kepler Chevreux also cut its target price on Amadeus to 39.20 euros from 43 euros, saying Lufthansa's move added uncertainties to Amadeus' outlook.