A major power outage at London's Heathrow Airport, caused by a fire at a nearby electrical substation, has led to the closure of the airport with no incoming or outgoing flights. The disruption is beginning to affect travelers in Atlanta, with a few flights canceled and potential delays for passengers connecting through London. The outage has stranded thousands of passengers globally, impacting flight crews and causing cancellations. Travel experts warn of significant schedule changes for Atlanta-based travelers heading to Europe through Heathrow, with delays expected to last for days as airlines work to rebook flights.