Hedges are (generally) option or commodity contracts. Write-downs involved are because of mark-to-market accounting- the contract is worth more the higher the price of fuel is. Writing it down isn't a bad thing -you purchasing hedged fuel at the same price no matter the cost of oil- it just means the firm backing the options don't have to pay as much to make up the difference between the hedge price and the spot price.

The value of hedges really shouldn't be included on a balance sheet- it's a contract that provides a predictable fuel cost for the future and is therefore IMO a cost of doing business, not an investment.