According to the airline TAP, the cancellations were caused by the bursting of the tires of a private jet, which forced the closure of the airport's runway.
In turn, the air controller ANA (Aeroportos de Portugal), claimed that the situation was the result of a broader problem of "constraints at several European airports."
"Due to a set of constraints at several European airports, 65 canceled flights are planned for today - 40 arrivals and 25 departures," ANA said in a statement sent to the press.
According to the company, Lisbon airport "implemented measures to support airlines, namely the installation of additional mobile counters to reschedule flights."
"We advise passengers with a scheduled flight to contact the airlines," said ANA.