British Airways and Air Berlin are to codeshare on more than 40 European flights from July 5.
BA customers can now buy direct flights on Air Berlin to Nuremburg, Munster and Paderborn through ba.com, with connections available from the main German gateways to destinations such as Palermo and Brindisi.
Air Berlin is to join the oneworld alliance next April.
British Airways' chief executive officer Keith Williams said: "The new Air Berlin services are the perfect complement to our existing European routes. Both airlines are committed to a full service offering and excellent value for money and this codeshare provides our customers with a preview of what is to come when airberlin officially joins oneworld next year."
