There were five flights to Spain - two for Barcelona and one each for Madrid, Valencia and Malaga - from Gatwick Airport on Monday May 24.
The country is on the “amber” list under the Department for Transport’s traffic light system, and government ministers have asked passengers not to fly to amber nations.
SEE ALSO UK condemns Belarus after Ryanair flight carrying opposition activist diverted | Airline Wizz Air UK takes off again from Gatwick Airport | Airline JetBlue to start service to New York from Gatwick in September | Gatwick's strong revival will create the business environment necessary to diversify the region’s economy, according to new report
Arrivals to the UK from amber list countries must self-isolate at home for 10 days and take two coronavirus tests.
Flights from the UK to Spain are set to double to around 80 a day this week, carrying an estimated 16,000 passengers.
Spanish Prime Minister Pedro Sanchez said last week: "Spain will be delighted, very delighted to welcome all British tourists".
"They are welcome to our country without restrictions and without health requirements."