NEW YORK (Reuters) – JetBlue Airways Corp said it has restored online booking and check-in after a power outage shut its main website for about two hours on Thursday, raising concern about delayed flights.

A maintenance operation disrupted power at a data center run by JetBlue’s business partner Verizon Communications Inc, the airline said in a statement, adding that this was not a “cyber security issue.”

Verizon has since restored power at the center, and JetBlue’s website is up for booking and check-in, the New York-based airline said in a blog post at 2:30 PM ET.

However, JetBlue said it was “still experiencing system issues” because of the outage.

JetBlue had 36 flight delays and four cancellations as of 3:00 p.m. EST, according to flight tracking website FlightAware.com.

The technical issue follows several high-profile computer problems that U.S. airlines experienced in 2015, including a router error at United Continental Holdings Inc and a malfunctioning iPad application used by pilots at American Airlines Group Inc.

Industry consultants say computer disruptions will have a growing impact on airlines, and their passengers, as they automate more operations, outfit their planes with Wi-Fi and distribute boarding passes on smartphones.

(Reporting By Jeffrey Dastin in New York; editing by Andrew Hay and Alden Bentley)