hangar was nearly complete by April 1939. The expanded North Beach Airport opened on October 15, 1939, and was officially renamed the New York Municipal Airport–LaGuardia Field later that year. Covering with nearly of runways, the airport cost $40 million, making it the largest and most expensive in the world at that time. The seaplane terminal comprised $7.5 million of this cost, and the hangar alone cost $2 million. The land-plane section of the airport opened for commercial flights on December 2, 1939, but the completion of the marine terminal was delayed until March 1940. This was in part because construction in Bowery Bay had prevented seaplanes from landing there. Seaplanes instead traveled to bases in Port Washington, New York, and in Baltimore, Maryland. Pan Am use At a hearing before the Civil Aeronautics Board in April 1939, Pan American Airways indicated that it planned to use North Beach Airport as the main U.S. terminal for the transatlantic flights of its Boeing 314 Clippers. Under this plan, Clippers would fly to Baltimore if there was bad weather in New York City. Pan Am leased the Marine Air Terminal from the New York City government the following month. Pan Am also allowed foreign airlines to use the terminal, including Imperial Airways, Air France, and KLM. Opening and early years The Marine Air Terminal officially opened on March 31, 1940, when a Clipper carrying ten crew members, nine passengers, and over 5,000 pounds (2,300 kg) of mail departed from the terminal. This flight landed in Lisbon, Portugal, 18 hours and 35 minutes later, setting a record for an eastbound transatlantic Clipper flight. The first flying boat to arrive at the Marine Air Terminal arrived from Bermuda on April 1, 1940. At the time, the terminal served three transatlantic trips per week. A brochure distributed on the terminal's opening day proclaimed it as "an enduring terminal linking the air routes of the old world with those of the new". Originally, members of the public were allowed to visit the Marine Air Terminal's observation deck, which became a popular place to observe seaplane and airplane landings. The deck was closed for security reasons during World War II. In July 1940, American Export Airlines and city officials began discussing the possibility of constructing a second seaplane hangar next to the Marine Air Terminal. American Export wanted to operate a transatlantic passenger route from LaGuardia Airport,