Iowa’s Attorney General is joining counterparts in 19 other states in opposing a proposed online reservation system for air travel. Tom Miller says the “Orbitz” system is supported by the five major airlines and others.Miller fears Orbitz would result in ticket-price collusion among the big airlines while further raising prices for Iowa air travelers.Miller and the other Attorneys General have sent a letter to top federal officials, urging them to prevent the airlines from joining forces on the combined online reservation system. Miller says Orbitz “has the potential to harness the vast power of the Internet for anti-competitive purposes.” A Justice Department spokesperson says Orbitz is still under review.