Aviation stocks prove popular in City

The FTSE 100 Index is up 27.7 points at 5346.5 at mid-morning.

Shares in British Airways are up 10% or 20p at 233p as traders await December traffic figures.

Investors have been cheered by upbeat data from Dutch airline KLM and Go - the low-cost airline sold by BA last year.

Aero-engine maker Rolls-Royce is up 5½p at 176¼p; while airports operator BAA is up 9p at 589p.

Tech stocks are still making gains, with chip designer ARM Holdings up 3% or 11½p at 393½p; software group Sage up 11¾p at 255p; Dimension Data up 4p at 93p; and Telewest Communications up 2p at 67p.

Marshalls, the construction products firm which supplied the paving stones for London's revamped Somerset House, has seen its share price rise by 8p to 251p after it said demand was on the up as people sought to landscape their gardens.

But shares in biotech firm PPL Therapeutics, which worked with the Roslin Institute to clone Dolly the sheep, are down 16% or 11½p at 62p following the announcement that Dolly has arthritis.

PPL's share price had risen by 46% on Wednesday to 77½p following the announcement of the birth of five cloned piglets which have a "knocked out" gene to prevent humans rejecting organ transplants.