AVMAN
I would imagine that since the fares are non-refundable they have no need to overbook. The seat is paid for whether the passenger turns up or not.
In theory yes. But with low cost tickets booked way ahead, there will usually be a fair percentage of no shows. Business travelers in particular often find it cheaper to book multiple low-cost non-refundable tickets than buy a flexible ticket with a major carrier.
And the temptation of low-cost carriers to get that bit of extra income on those empty-but-paid-for seats is just too much to resist.
