Failed runway lights caused a blackout at Glasgow International Airport in the UK, forcing four planes to abort landings and delaying the landing of eight others, on Monday.

According to the dailyrecord website, the blackout affected the guide lights across the airport’s tarmac, which also caused havoc for outbound flights.

Engineers at the airport followed contingency plans and switched to a manual system but flights were still delayed.

According to airport officials, the cause of the blackout has not been identified yet and the airport authorities are investigating the issue.