(CNN) -- An American Airlines plane made an emergency landing Tuesday night in Orlando after the crew noticed a crack in the cockpit windshield. American Airlines Flight 160, with 150 passengers and six crew members, took off from Miami and was headed to Boston, said airline spokeswoman Andrea Huguely. The Boeing 757 had reached cruising altitude when the crew noticed a crack on the exterior window of the double-paned cockpit windshield, Huguely said. The size of the crack, or the cause, was not immediately known. The pilot declared an emergency, and the plane landed in Orlando. Emergency landing after part of plane flies off . Southwest plane returns to Nashville after striking birds . Plane blows engine, loses power . CNN's Chuck Johnston contributed to this report.
The plane was carrying 150 passengers and six crew members . The flight was headed to Boston .