Load factor
Forgive if I'm mistaken, but...
The purpose of load factor is to give a measure of how many available seats were sold for revenue that can be recognised formally in the accounts.
On many airlines (e.g. full service carriers), many tickets sold are refundable after the plane has departed. Because a customer need not apply for a refund until quite a while later, it is not possible in any given calendar month to know exactly how many refunds will need to be given. The easy way to measure how many seats are sold with recognisable revenue is to count physical bums on seats - thus load factor. Perhaps overly conservative as a measure but very easy to measure.
If as with Ryanair, an airline has a policy of never selling tickets that can be refunded / changed after a missed departure, the proportion of earned seats is probably a better measure of how well sales are going between months or years. Treating this as equal to load factor however is not correct.
My bugbear is when seats are sold for 1 penny or 1 eurocent. Because money changes hands and thus there is consideration, the law recognises this as a contract and thus a ticket is legally deemed to have been sold. Treating these as earned seats in monthly reporting I think is incorrect.
IMHO, an airline should count only seats where the total sale price is at least the value of Govt tax, airport charges and any other obligatory fees on a per pax basis - a sale price below that should be reported as a non-revenue or subsidised ticket