The FAA is investigating an emergency landing by a Spirit Airlines flight after the crew reported the aircraft was struck by lightning twice just after takeoff from Philadelphia.

Spirit says the Airbus A321 en route to Cancun turned back to Philadelphia International Airport “out of an abundance of caution after the crew reported a suspected lighting strike.”

“The aircraft landed safely, and we are currently working to reaccommodate our guests,” Spirit said in a statement to CNN. The airline did not say how many passengers were on board.

LiveATC air traffic control recordings capture the exchange between the flight crew and Philadelphia air traffic controllers. “We were struck by lightning twice,” said the crew. “We’re gonna have to come back to the airfield.”

The Federal Aviation Administration says the incident happened at 11 a.m. local time Friday and that the agency will investigate.

The incident is the latest impact from a storm that has caused more than 4,000 flight cancellations nationwide on Friday, according to FlightAware data. Airlines have issued travel waivers for many parts of the US allowing passengers to rebook without penalty for a short window.