BMI British Midland has become the first airline to put a balance sheet value on its take-off and landing slots – inflating its net asset value by £770m. As the group reported a halving of profits for last year on the back of a lossmaking acquisition and spiralling fuel costs, BMI said its “conservative” valuation of the Heathrow slots had helped raise the value of its net assets from £12m at the end of 2006 to £800m at the end of 2007.

Analysts said BMI’s new approach, which could be copied by other airlines, gave the company an easier route to the debt markets.