German carrier Deutsche Lufthansa AG (LHA.XE), which owns 80% of British Midland Airways, or bmi, Thursday said its holding company LHBD Holding Ltd. would buy the remaining 20% stake in the U.K. carrier from Scandinavian airlines SAS AB (SAS.SK).

Lufthansa will pay SAS GBP19 million for its stake and a further GBP19 million for cancelling rights that date back to a shareholder agreement in 1999.

Lufthansa will also have to pay SAS an additional payment should the German carrier sell all or parts of bmi within the next two years. At the same time, SAS will have a GBP19 million maximum exposure in bmi for the next two years in the event of "material adverse financial development of bmi and lack of financial support from Lufthansa," SAS said.

Lufthansa earlier this year raised its stake in the airline to 80% after bmi founder Michael Bishop threatened legal action to force the carrier to complete its take-up option and buy his stake of 50% plus one share. The put option was originally agreed in 1999, but Bishop exercised the option last October just as the global aviation industry took a turn for the worse. Once Lufthansa increased its stake it was forced to make an offer to SAS for the remaining shares.

The German airline holds a 35% stake in U.K.-based LHBD, but will raise that stake to 100% once it has obtained the necessary traffic rights for bmi at no cost.

Bmi has faced financial challenges, which were exacerbated by the surge in oil prices last year and the global economic crisis. However, at least 12 airlines have approached Lufthansa voicing their interest in bmi, mainly for the 11% of takeoff and landing slots it holds at London's Heathrow Airport. Bmi is the second largest carrier at operating at Heathrow airport after British Airways PLC (BAY.LN).

Heathrow slots are the most sought-after in the industry, especially since the Open Skies deal was agreed in 2008 allowing carriers in the U.S. and Europe to fly from and within the U.S. or Europe. Airlines' growth at Heathrow is dependent on trading slots as there's little opportunity for capacity to expand without a third runway. But slots don't come on the block often and are expensive, making it difficult to enter or grow at Heathrow.

Lufthansa's priority is to restructure loss-making bmi, together with bmi's management, so that it can command a higher price for the airline should it sell it as a whole. Other options include selling parts of bmi and keeping some Heathrow slots to secure Lufthansa's own growth at the airport, or even keeping the airline itself.

U.K. carriers British Airways and Virgin Atlantic have already publicly voiced their interest in bmi. Another potential bidder could be Flybe but mainly for bmi's regional assets. A spokesman for Flybe declined to comment.

Potential bidders may be deterred from bidding for bmi as a whole because of the uncertainty surrounding the current size of its pension deficit and the challenges in dealing with those liabilities and unions when trying to cut costs.

A spokesman for bmi Wednesday declined to reveal the size of bmi's deficit as its accounts have yet to be filed.

The last set of accounts filed show the net pension plan deficit stood at GBP45.8 million on Dec. 31, 2007.

At 0810 GMT SAS shares traded up SEK0.05, or 1% at SEK5.00, while Lufthansa's shares traded down 2 cents, or 0.2%, at EUR12.09.

-By Dominic Chopping, Dow Jones Newswires; +46-8-5451-3093; dominic.chopping@dowjones.com; Kaveri Niththyananthan, Dow Jones Newswires; 4420 7842 9299; kaveri.niththyananthan@dowjones.com