Passenger traffic at BAA airports dropped 1.7 percent in June year-on-year, hit by the series of walkouts by British Airways cabin crew.

But air freight, a reliable barometer of the health of world trade, rose 21.7 percent across BAA’s six airports, with the figure for 2010 so far well up on last year.

BAA operates six airports in the UK – Heathrow, Stansted, Glasgow, Edinburgh, Aberdeen and Southampton. The airports operator – which is majority-owned by Spanish firm Ferrovial – sold Gatwick for £1.5bn last year.

It said that 9.5 million passengers flew from its airports last month, down from 9.7 million in June 2009.

Glasgow suffered the worst decline, down 7 percent year-on-year. South of the border, London Stansted was the hardest hit – traffic down 5.2 percent. However Heathrow remained roughly in line with the same month last year, with 5.78 million passengers.

The figures follows last week’s announcement by British Airways that it carried 11.1 per cent fewer passengers in June compared with the year before due to the walk-outs, which affected the first nine days of the month. The total cost of strikes is estimated at £150 million.