Had an early miscarriage

Coldn get pregnant for 8 years and using this app had intercorse on the day that it showed I'm fertile 18,2% . After that I had I 13 hours flyght. I was late to get my period, test showed negative week later I start bleading , wasn't normal. Blood was black and 2 days later the big black ( like blood cloth) came out ! As much as I research, now I understand that I didn't have a late period, but it was miscarriage! It has been 3 days and with everyone is hurder and mind blowing. I'm trying to understand why it happend. Wondering if flying had to do something with it?
Thank you , who will write something. I am 34 years old. Still no kids :(