The extent to which the pre-Christmas cold spell severely affected flight punctuality at major UK airports was revealed in official figures out today.

The number of flights on time and the average delays worsened sharply in December 2009 compared with December 2008, the statistics from the Civil Aviation Authority showed.

Punctuality of charter flights in December 2009 at the five London airports - Heathrow, Gatwick, Stansted, London City and Luton - was only 47%, a drop of 5% on the December 2008 figure.

The decline was even worse at the regional airports surveyed - Birmingham, Manchester, Newcastle, Edinburgh and Glasgow - where the on-time flight percentage went down 12 points to 52%.

Scheduled flight punctuality at the London airports was down 9% in December last year compared with December 2008, while regional airports' performance dipped 10%.

Despite the poor December 2009 figures, punctuality of charter flights in and out of the 10 airports surveyed improved from 67% in the period October-December 2008 to 71% in the last three months of 2009.

The average delay to charter flights during the last three months of last year was 24 minutes - the same as the figure for the last quarter of 2008.

Scheduled flight punctuality at the 10 airports dipped from 79% in October-December 2008 to 77% in October-December 2009, with the average delays rising from 12 minutes to 15 minutes.

Of routes with a high passenger density, Rotterdam had the best on-time performance in the last three months of last year, at 90%.

The worst route for punctuality was Istanbul where only 44% of scheduled flights were on time in October-December 2009, with the average delay being 32 minutes.