
Airports impacted include popular holiday hotspots such as Lanzarote, Fuerteventura, La Palma and El Hierro, alongside mainland hubs including Seville, Madrid, Vigo and Jerez.
The strike targets control towers operated by private firm SAERCO, which manages services at a number of busy regional airports, particularly during peak travel periods.
They also accused the company of cancelling approved holidays, making last-minute shift changes and failing to provide clear schedules for mandatory breaks.
Travellers have reported long queues of up to three hours at security, with some flights departing without passengers' luggage and others missed entirely due to delays.
With Spain remaining one of the most popular destinations for British tourists, the latest strike threat is expected to cause significant disruption during the busy spring and summer travel period.
Passengers are being advised to check with airlines before travelling and allow extra time at airports as the situation develops.