Not everyone requires 5 years. Air Evac (in Texas - san antonio area) requires 3 years and passing their test. I volunteered as an EMT-B then an EMT-I85 in texas with a third service 911 and a volunteer firefighting company. My prehospital experience was MINIMALLY relevant. I was asked one question about it in my interview, to which my answer was, i have earned my NREMT-I85. Get, Your TNCC and an EMT-B and you will be solid for what you "need to know" about scene work and concentrate on ther critical care aspects. Try to get in on a CVICU or a CCU that runs a lot of balloon pumps/impella/ or ECMO. Those skills will translate greatly to what a potential flight company (that does interfacility CCT). But DO get a least a year or two in the SICU. That will also help greatly.