It comes as the German airline reported a net loss of €8m (£6.3m) in the three months to the end of March against a profit of €425m a year earlier.
The airline said it would now grow the number of seats it offers by 6% this year instead of 6.6%.
It said it would also look at whether further cost cuts needed to be made.
In March, Lufthansa said it would resume dividend payments to shareholders and forecast slightly higher profits in 2016.
The airline confirmed those forecasts on Tuesday, despite saying profits at its cargo unit would be significantly below those of the year before.
Last week, British Airways owner International Consolidated Airlines Group said it would temporarily slow plans to fly more routes. This was due to the impact of the Brussels terror attacks on travel, and also a result of weaker demand from high-margin business travellers.
Lufthansa's chief financial officer Simone Menne said yields - a measure of revenues per mile per passenger - fell 5.4% in the quarter.
However. she said that the group had not seen a substantial financial impact since the terror attacks in Paris and Brussels.
Lufthansa is still trying to bring costs down at its main brand to compete more effectively with low cost carriers in Europe.
It is also coming under pressure from Middle East rivals on long-haul flights and has been in a long-term dispute with pilots and cabin crew as a result on a new pay and pension deal.
Last year, it was hit by strikes by both pilots and cabin crew, which cost Lufthansa €231m in lost earnings.
Lufthansa has said it will slow the pace of its growth plans this year as it continues to come under pressure from lower cost competitors.