Weekly Wednesday flights from Birmingham will get under way on 13 May 2020 and will operate through 30 September.
At Manchester, meanwhile, Jet2 will launch twice-weekly Skiathos services in early May, running through to late September.
Jet2 will also fly to Barcelona from Birmingham for the first time next year, promising a twice-weekly service.
In total, Jet2 will launch seven new destinations from Birmingham next year, and four from Manchester.
Birmingham’s other new destinations are Preveza, Budapest, Kefalonia, Nice and Murcia.
Manchester is also gaining a Preveza link, as well as flights to Zadar in Croatia and Tivat in Montenegro – Jet2’s first route to Montenegro.
Jet2 will base an additional three aircraft at Birmingham for summer 2020, boosting capacity by 160,000 seats (23%).
At Manchester, it will base an additional four aircraft boosting capacity by 450,000 seats (16%).
Steve Heapy, Jet2.com and Jet2holidays chief executive, said the moves followed “unprecedented demand” for Jet2’s flights and package holidays. “This major expansion underlines our commitment to giving local holidaymakers the very best choice,” he said.
Jet2 will fly to 47 destinations from Birmingham next summer, and 50 from Manchester.