Shares in airlines fell in early trade as investors worried about the impact of the Barcelona terror attack on tourism.
British Airways owner IAG and EasyJet were both down by more than 2%, making them the biggest fallers on the FTSE 100 index.
The UK’s benchmark share index fell 51.40 points, or 0.7%, to 7,336.47.
Elsewhere in the travel and tourism sector, shares in Intercontinental Hotels Group were down 1.5%.
Analysts said there was also a broader sell-off on the market, following big falls on Wall Street on Thursday.
The US S&P 500 share index dropped 1.5% on Thursday – its biggest daily percentage drop for three months – over concerns that the Trump administration will not be able to deliver promised economic reforms.
On the currency markets, the pound was up 0.2% against the dollar to $1.2892, and was also 0.2% higher against the euro at 1.0997 euros.