Spanish officials warned Heathrow passengers they could be faced with days of disruption if the incident continues.
Aena, the airport operator in Spain, has said that even though British authorities confirmed that the fire had been contained, flight changes may continue for several hours or days.
Aena advises passengers to check with their airline if they have a connection to or from London.
READ MORE Heathrow Airport’s closure for 24 hours has created chaos in Spain.
A fire at an electrical substation forced London Heathrow to close the airport for 24 hours, resulting in 54 cancellations of flights to and from Spain.
The 54 affected flights were spread across Madrid, Barcelona, Malaga, Tenerife South and Valencia.
On Friday, a total of 1,351 takeoffs and landings are scheduled.
Terminals T2and T4 were completely without power and forced to suspend their operations.
British Airways, Iberia Express and Vueling are the three most affected airlines that have Spanish connections due to their concentration in the affected terminals.
Aena has also reminded impacted passengers that they can claim financial compensation between €250 and €600, if the legal requirements are met.
This is based upon flight distance and the waiting time and falls under EU Regulation No. 261/2004.