Flying with non faa/car car seat

Hi guys,

need some help on this topic 

I’ve booked tickets for myself and baby to fly to Poland with a car seat. At the time of booking I was unaware that there were such things as flight approved car seats 

i already be a perfectly fine car seat to use and dont have the funds to by another 

has anyone flown with a non approved car seat without any issues? 

Would love some advise on this issue 

thanks x