( CNN ) A Delta airplane had a close call Thursday , skidding off a snowy runway and stopping within feet of icy waters . Any accident raises questions , and the National Transportation Safety Board is sending people to New York 's LaGuardia Airport to investigate . Although the cause of the crash is not yet clear , officials will no doubt be looking at the conditions on the runway . Was it cleared and ready ? Did the pilot have all relevant information ? CNN aviation analyst Mary Schiavo breaks down the responsibilities around runways . `` There are a couple of things that airports have to do , '' she said . `` The airport has to go out and measure whether the airport runways have friction , meaning when those tires touch down that they will have some contact with the runway . '' That information is then relayed to the air traffic control tower , according to Schiavo . `` As to whether the runways are slippery , that is breaking action , and the airport gets that from the reports of previous pilots , '' she said . Port Authority of New York and New Jersey Executive Director Patrick Foye told reporters that the runway in question had been plowed shortly before the incident . Pilots on previous planes reported `` good braking action , '' he said . Just minutes after the Delta plane landed , all of LaGuardia Arport shut down to air traffic . One runway reopened at 2 p.m . ET . The other remained closed . Miles O'Brien , another CNN aviation analyst , highlights how difficult it is to understand all the elements in play . `` The wind was changing . The temperatures were changing . It was moving from rain to freezing rain , ultimately into snow . So you had a very dynamic weather picture , and let 's not forget , it 's kind of a subjective thing , '' he said . `` One pilot might say , 'oh that was no problem , ' but he might have learned how to fly in northern Canada . ''
Port Authority chief : Runway was just plowed , other pilots reported `` good braking action '' The NTSB is sending people to New York 's LaGuardia Airport to investigate .