(Reuters) – Delta Air Lines Inc Chief Executive Officer Ed Bastian on Thursday apologized for flight cancellations that have hit summer plans for many travelers, adding that it would take some time for disruptions to subside.

The airline has canceled over 400 flights since Monday, as per flight-tracking website Flightaware.com, amid bad weather and an industry-wide staff shortage that has not spared even the U.S. aviation regulator.

“If you’ve encountered delays and cancellations recently, I apologize,” Bastian said in a LinkedIn post. (https://bit.ly/3a2qtLA)

“Things won’t change overnight, but we’re on a path towards a steady recovery.” he added. 

Delta has flown over 96% of its scheduled departures in June, Bastian said, as the airline works to speed up hiring. The company has recruited 15,000 new employees since the beginning of 2021.

Bastian said the company is continuing to speak with the Federal Aviation Administration to improve air traffic management.

“The environment we’re navigating today is unlike anything we’ve ever faced,” Bastian said.

Persistent staffing shortages, fewer flights and booming demand have cast a shadow on the busy July Fourth holiday weekend and the entire summer travel season.

Analysts and some industry executives don’t see a meaningful improvement in conditions before fall, when travel demand tends to slow down.

Shares of Delta were down about 1.8% in afternoon trade.

(Reporting by Nathan Gomes in Bengaluru; Editing by Shailesh Kuber)