Because my son did not inspect his propellers prior to lift off and one wasn't on properly. I also noticed on his other MP1 cracks in the blades, hairline but still cracks... Double, triple check those blades.. His MP1 is fine, lucky for him he fall into a bush the softened up the crash. My MP is also ok but now that I just got my M2P I dont think I will be flying the MP1 very much.