Almost 400 flights were cancelled, affecting more than 55,000 passengers. Pilots in Ireland, Germany, Sweden and Belgium stopped work for 24 hours over pay and working conditions.
They were joined by Dutch pilots after an unsuccessful attempt by the airline to obtain a court order blocking the strike.
To add to the problems, on Friday, many thunderstorms were spread across the northern Mediterranean from the Balearic islands to the coasts of southern France and northern Italy.
As a result, easyJet cancelled around 30 flights, affecting about 5,000 people. British Airways made many cancellations, mainly to and from Heathrow, and delayed about a dozen planes overnight in various locations.