The budget airline told the union the decision to close the base, which operates 10 aircraft in summer, was part of wider planned cuts flagged last week due to weaker earnings, the grounding of the Boeing 737 MAX and concerns over Brexit, said SNPVAC director Fernando Gandra.

The timing "appears at least strange as it comes within days of our calling a strike in Portugal and as the company is telling staff its passenger numbers have risen 9% in July from a year earlier," Gandra said.

"We are looking into the matter and collecting data to see if it could be retaliation for the strike," Gandra said.

Faro airport serves Portugal's Algarve region which is popular with tourists, especially from Britain.

A Ryanair spokesman contacted by Reuters would not confirm or deny the closure, but said, as previously announced, that "a number of Ryanair bases will be cut or closed this winter" mainly due to the late delivery of up to 30 Boeing 737 MAX aircraft.

"These consultations are taking place with our people at affected bases currently. No routes will be affected as they will be served by flights from other bases from November when the winter schedule starts," he said.

The SNPVAC union on Aug. 1 said its members would go on strike for five days from Aug. 21 after Ryanair refused to comply with a protocol signed last November, which it said included holiday pay, 22 days of annual leave per year and full compliance with Portuguese parental law.

A day earlier, Ryanair Chief Executive Michael O'Leary told staff in a video message that the company had 500 more pilots and 400 more cabin crew than needed, and that job losses would be announced in the coming weeks.

Ryanair currently operate around 2,400 daily flights from 87 bases.

(Reporting by Andrei Khalip and Padraic Halpin; editing by Axel Bugge and Jason Neely)