Air travellers are experiencing significant disruptions at several European airports, including Heathrow, due to a cyber-attack that affected check-in and baggage systems. Hundreds of flights were delayed, with some airlines resorting to manual check-in methods. Brussels Airport has asked airlines to cancel half their departing flights, while Heathrow continues to operate with a backup system for British Airways. The situation is ongoing, with various airports managing delays and cancellations.