A power outage at Delta Air Lines’ Atlanta hub and the impact of a winter storm hit the airline’s last quarter 2017 profits by $60 million.

The carrier still achieved quarterly adjusted pre-tax income of $1 billion.

However, Delta reported a $621 million drop in annual profits to $5.5 billion over 2016.

This came as full year operating revenue rose by 4% to $41.2 billion.

Delta, Virgin Atlantic’s US partner, spent $450 million to take a 10% stake in Air France-KLM in the final three months of 2017.

CEO Ed Bastian said: “Delta people rose to the challenges of 2017 to produce solid financial results, industry leading operational reliability and strong improvements in customer satisfaction, and it’s an honour to recognize their achievements with $1.1 billion in profit sharing.

“Looking ahead to 2018, we expect to drive solid earnings growth by growing our top line 4% to 6%, improving our cost trajectory and integrating our international partner network.

“As a result, we are able to increase our previous full-year guidance to $6.35 to $6.70 per share due to additional benefits from tax reform.”

Delta president Glen Hauenstein added: “We enter 2018 with significant momentum and every entity delivering positive passenger unit revenue for the first time in five years, driven by a robust demand environment and improving business fares.”