The first KLM [trial-] New York flight departed AMS on 25 Feb 1946 using DC-4 Skymasyter NL-305, with US captain McClure.
Regular service [twice weekly] was started at 21 May 1946 by the DC-4-1009 "Rotterdam", captain was Evert van Dijk [who also flew the very same route 16 years before with Sir Charles Kingsford Smith in Fokker F.VIIB/3m "Southern Cross"]. The New York flights made en-route stops in Prestwick and Gander for a total travel time of 25 hrs 30 min [net flight time 21 hrs] one way.
Since JFK [Idlewild] was not yet open to business at the time, all KLM flights operating to New York were using North Beach Airport, which in 1947 became La Guardia Airport. I believe that KLM started using Idlewild [today JFK] only in 1948, so KLM did operate transatlantic service into LGA in 1947 and 1948!
I was wondering if other European airlines also operated into LGA, and which trans atlantic services were operated from LGA by which airlines.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
"....BOAC needed modern aircraft for its trans-Atlantic route to New York's La Guardia. BOAC had been using the Boeing 314 flying boats but these were retired in March after which the route was ceased. The British Government gave the airline permission to purchase five Lockheed L-049 Constellations to restart the route. The Connies began this route twice-weekly from 1 July 1946.........In December 1949 BOAC also introduced the Boeing 377 Stratocruiser for the trans-Atlantic service. The Stratocruiser had a bar and lounge and gave a luxurious touch to the 17 hour flight. In 1950 these trans-Atlantic flights were transfered from La Guardia to New York's second airport, Idlewild (now called JFK)."