I don't know really which airlines are safer than others, but Allegiant doesn't seem to be all-out dangerous as their reputation led some to believe. I fly them fairly often on OAK-AZA and they are usually close enough to on time. If something mechanical happens with the plane then you will take a longer delay than some airlines (I've had 4-5 hour delays). In those circumstances Allegiant has proactively sent me a voucher via email before the plane even left the ground equal to the price of my fare. I think that's pretty decent.