Investing.com - Deutsche Bank (DE:DBKGn) says the growing trade dispute between the U.S. and other countries could mean "collateral damage" for the American airline industry.The Wall Street firm downgraded its ratings on the three biggest U.S. airlines -- Delta, American and United Continental -- from buy to hold and also trimmed its price targets for them. In a note to clients, Deutsche Bank said the big three are particularly vulnerable to trade fallout because of their large global networks and reliance on corporate travelDeutsche said U.S. companies could cut corporate travel if the trade situation prompts them to reconsider their spending and employment plans. The firm also lowered its price forecasts for four other airlines, but kept its buy rating because their business is domestic-oriented.U.S. airlines had a strong start to the year, but a jump in jet fuel prices has since cut into profits.The popular U.S. Global Jets exchange traded fund is down 16% from its January high.