A jet carrying 60 passengers and four crew members collided Wednesday with an Army helicopter while landing at Ronald Reagan National Airport near Washington, prompting a large search-and-rescue operation in the nearby Potomac River. There were multiple fatalities, according to a person familiar with the matter, but the precise number of victims was unclear as rescue crews hunted for any survivors. Three soldiers were onboard the helicopter, an Army official said. There was no immediate word on the cause of the collision, but all takeoffs and landings from the airport were halted while helicopters from law enforcement agencies across the region flew over the scene. Inflatable rescue boats were launched into the Potomac River from a point along the George Washington Parkway, just north of the airport, and first responders set up light towers from the shore to illuminate the area near the collision site. The Federal Aviation Administration said the midair crash occurred around 9 p.m. EST when a regional jet that had departed from Wichita, Kansas, collided with a military helicopter on a training flight while on approach to an airport runway. It occurred in some of the most tightly controlled and monitored airspace in the world, just over three miles south of the White House and the Capitol.