The NTSB has an explanation for why the front wheel of a Boeing 737 “popped off” as the plane was landing at LaGuardia on Monday evening. Jets are supposed to come down on their rear landing gear first, but Flight 345 from Nashville came down nose first, causing the front landing gear to collapse, according to the Associated Press. Southwest said the landing is “is not in accordance with our operating procedures.” The nose was pointed two degrees upward four second before impact, and it’s unclear what caused it to tip downward at the last second. The plane skidded for nineteen seconds and eleven people were injured. When asked if the findings indicate pilot error, an NTSB spokesman said the investigation has not been completed.