Proctor had spent the whole day off-duty and had flown the initial Los Angeles to San Francisco leg of the flight. Accident history Flight 845's crew had planned and calculated its takeoff for runway 28L but discovered only after pushback that this runway had been closed hours earlier for maintenance, and that the first of runway 01R, the preferential runway at that time, had also been closed. After consulting with Pan Am flight dispatchers and the control tower, the crew decided to take off from runway 01R, shorter than 28L, with less favorable wind conditions. Runway 01R was about long from its displaced threshold (from which point the takeoff was to start) to the end, which was the available takeoff length for Flight 845. Because of various misunderstandings, the flight crew was erroneously informed that the available takeoff length from the displaced threshold was , or longer than actually existed. Despite the shorter length, it was later determined that the aircraft could have taken off safely if the proper procedures had been followed. As the crew prepared for takeoff on the shorter runway, it selected 20 degrees of flaps, instead of the originally-planned 10 degree setting, but did not recalculate the takeoff reference speeds (V1, Vr and V2), which had been calculated for the lesser flap setting and were thus too high for their actual takeoff configuration. Consequently, the critical speeds were achieved late and the aircraft's takeoff roll was abnormally prolonged. In fact, the first officer called Vr at , instead of the planned , because the end of the runway was "coming up at a very rapid speed." Damage Unable to attain sufficient altitude to clear obstructions at the end of the runway, the aircraft had its aft fuselage, landing gear, and other structures damaged as it struck components of the approach lighting system (ALS) at over . Three lengths of angle iron up to penetrated the cabin, injuring two passengers. The right main under-body landing gear was forced up and into the fuselage, and the left under-body landing gear was ripped loose and remained dangling beneath the aircraft. Other systems damaged in the impact included No. 1, 3, and 4 hydraulic systems, several wing and empennage control surfaces and their mechanisms, electrical systems including the antiskid control, and three of the evacuation slides. The flight proceeded out over the Pacific Ocean for 1 hour and 42 minutes