The sale of GB Airways to easyJet has left four pairs of slots for grabs at Heathrow.
The disposal of the former BA franchise to the UK low cost carrier for £103.5m cash excluded the four slots at the congested airport.
The Bland Group, which owned GB, has now handed them to the safekeeping of Airport Co-ordination Limited (ACL).
Their next owners are likely to be decided at the International Air Transport Association (IATA) conferences in Toronto on November 9-13.
Sought after slots, like these ones, have in the past fetched up to £20m each.
Two American carriers NorthWest Airlines and Continental Airlines are among those which have indicated they wish to start services from Heathrow when the US-EU Open Skies agreement comes into force next March.
A spokesman for Continental declined to comment on whether it was in the market for any of the GB slots.
But its president and ceo Larry Kellner recently said that he wanted to start a "minimum" of three services from Heathrow next year. Destinations are likely to be Newark New York and its hub at Houston.
It is also likely that BA, which already owns 41% of the slots at the airport, would be interested in buying any of the GB slots.
GB is a point to point airline which serves 39 destinations in southern Europe and North Africa.
It flew mainly out of Gatwick but had a small number of services from Manchester and Heathrow. It previously operated under a franchise agreement with BA.
easyJet said the acquisition was consistent with its expansion strategy.
Andy Harrison, the airline's ceo, said: "This is an acquisition which both strengthens our customer offering at London Gatwick, our biggest base with an attractive catchment area, and allows us to fully capitalise on the potential of the airport through a larger number of slots.
"The deal will bring major benefits to both easyJet and GB Airways customers, delivering a wider choice of destinations."
The sale also marks the end of BA's franchise agreements.
The airline said the GB deal would finally end in March 2008 while another franchise agreement with Scottish carrier Loganair will end next October.
Willie Walsh, BA's ceo, said: "UK franchises have outlived their purpose. easyJet has made an offer to buy GB Airways and this has enabled us to end the franchise agreement early. We had an option to buy GB Airways but we rejected it.
"We have a significant base at Gatwick and our focus will be on maintaining and developing it as an integral part of our business."
The UK carrier said it planned to start its own services to some of the GB destinations, among them Faro, Malaga, Gibraltar, Ibiza, Palma and Tunis.
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