The DC-6, named “Mainliner Idaho”, took off from New York-Idlewild at 14:28 for a captain instrument proficiency check flight in the vicinity of Islip. At 15:27 the flight was cleared for an ILS approach to Islip-MacArthur Field. After landing the crew were cleared to taxi into position at runway 32. Takeoff clearance was given at 15:48 and 15:50. When climbing through 50 feet the right wing dipped and the DC-6 turned to the right. The climbing turn continued with an increasing bank angle. Bank angle was about 90deg when climbing through 150 feet. Control was lost and the aircraft dived into the ground. A fire broke out. PROBABLE CAUSE: “Unintentional movement of no.4 throttle into the reverse range just before breaking ground, with the other three engines operating at high power output, which resulted in the aircraft very quickly becoming uncontrollable once airborne.”