By Alvaro Murillo SAN JOSE (Reuters) – Costa Rica’s Juan Santamaria International Airport will remain closed until 6 p.m. local time on Thursday after a Boeing 757-200 cargo aircraft operated by DHL made an emergency landing before skidding off the runway and splitting, aviation authorities said. The pilot and copilot were evacuated, airport operator Aeris said in a statement. Costa Rican newspaper La Nacion tweeted images showing the yellow aircraft emblazoned with DHL with its tail detached and a broken wing, being doused with firefighting foam as its lay partly in a grass field and the runw…