International Airlines Group, parent company of British Airways and Spain-based Iberia, on Friday reported falling revenues during the first six months of 2016. Passenger unit revenues (defined as passenger revenues per available seat kilometer) fell 10.2 percent, to €6.67 ($7.17). At the same time, profitability received a boost from additional income from the recent acquisition of Ireland’s Aer Lingus.

Net profit (after tax) for the first half of 2016 climbed by 67 percent, to €554 million ($595 million). In the second quarter alone, operating profits stood at €555 ($596 million)—4.7 percent up on the same period in 2015. However, without the contribution from Aer Lingus profits would have fallen 8 percent, to €487 million ($523 million).

Commenting on the mixed results, IAG chief executive Willie Walsh said that multiple factors have converged to make for “a softer than expected trading environment.” Those factors included economic uncertainty around the UK’s June 23 vote to leave the European Union (EU), currency exchange rate instability, multiple terrorist attacks across Europe, weakening economies in Latin America, Spain’s general election and operational disruption caused by no fewer than 22 European air traffic control strikes so far in 2016.

Similar factors appear to have negatively affected the performance of several other European carriers. Announcing first-half results for 2016 on July 27 for Air France-KLM, chief financial officer Pierre-François Riolacci indicated that the airline has seen a significant decline in demand for flights into Europe, and especially into France, which has suffered multiple terrorist attacks. However, while second quarter revenues dipped by 5.2 percent to €6.22 billion ($6.7 billion), the group achieved a better-than-expected operating profit of €317 million ($341 million), representing a 77 percent improvement on the same period in 2015.

On July 25, Ireland-based low-cost carrier Ryanair, which uses a different fiscal reporting period, reported a 4 percent increase in first quarter profits to €256 million ($275 million). The company indicated that performance would have been stronger were it not for the effects of terrorism and the cost burden of air traffic control disruption. Chief executive Michael O’Leary commented that while its overall growth plans will continue, Ryanair likely will scale back expansion in the UK market, which he said will see weakened demand in response to uncertainty over the country’s future relationship with the EU.