Lufthansa gave a gloomy outlook for the key summer season and said it would focus on reducing costs after attacks in Europe deterred travellers from booking trips.

“We don’t have any visibility on how people are booking, and we’re losing group bookings from Asia and the United States due to travel warnings,” chief financial officer Simone Menne told journalists.

The uncertainty comes during the third quarter for European airlines, traditionally when they make most of their money due to the summer holidays.

Last week Air France-KLM said it was concerned about France’s attractiveness as a destination, while British Airways owner IAG gave a cautious outlook for the year.

Ms Menne said Lufthansa had sold 67 per cent of seats for the third quarter, three per cent less than at this time last year.

Unit revenues are set to fall eight to nine per cent in the second half, and yields – a measure of pricing – are at levels last seen during the 2009 financial crisis, CEO Carsten Spohr said.

Its shares, down almost 30 per cent this year, dropped 3.8 per cent, the biggest fall among European travel and leisure stocks.

Lufthansa, which has been trying to reduce costs in the light of competition from low-cost carriers and fast-growing carriers such as Emirates and Turkish Airlines, said it aimed to reduce unit costs, excluding fuel and currency, by between two and three per cent in the second half of the year.

“With the recent market developments, the importance of efficiency gains is prioritised... In 2017, the focus will be on cost efficiency and not growth,” Mr Spohr said.

In the first half, unit costs fell 1.3 per cent. Lufthansa has agreed a new pay and pensions deal with cabin crew but is still in talks with its pilots.

Lufthansa expects 2016 adjusted earnings before interest and tax (Ebit) to be below that of last year, when it made just over €1.8 billion.